I don’t think this is a totally crazy metaphor. I think it’s mostly crazy.
Let me deal first with the instance in which I think it is not crazy. The way heaven is pictured in some of the slave songs of the American south is not all that different from some of the prophetic accounts of what this world will be like when God establishes His reign fully. This is a picture generated and sustained by a people in slavery.
The common term is that God will make things right. The difference is that in the first, there is a Realm where “rightness” is the natural and necessary condition; in the other, ‘rightness” will be established here, where iniquity now rules. The notion of heaven has a place in those conditions, I think, and that’s why I am not going to call the metaphor of heaven as some kind of dessert entirely crazy.
Heaven is, of course, no one’s desert. No one deserves heaven.
The celestial  metaphor I want to work with is you get dessert if you finish your dinner—particularly if you finish your vegetables. Why is it always vegetables?
The deal here is that the meal is disagreeable, but there are compensations for putting up with it.
Just to set them aside, let’s eliminate some reasons why the meal is so bad that you have to be bribed to finish it. The first is that it isn’t really bad; it’s just that you have not yet developed an appreciation for it and you will if you have continued experiences with it. The second is that it could have been good except that somehow, salt got used where menu called for sugar. The third is that a lot of good ingredients were ruined by ignorant and/or uncaring preparation and the only reason you have to eat it is some odd moral insistence on “finishing things properly.”
All those situations have their obvious remedies. None of them are what I am talking about.
The distinction at the heart of this veggies/dessert distinction is that you don’t like veggies. That is why you have to be bribed to eat them. But imagine, instead, that you are talking about a lowly job in a sequence of jobs and that you have your heart set on the highest one. The phrase that is often used in such a situation is that you have “paid your dues.”  You get to seek a higher job because you have done a lower job. There is the little problem of what is higher and what is lower, but we’ll waive that for the moment.
The lowly job which is a down payment on the more exalted job is better than the veggies/dessert distinction, but it doesn’t really address the problem.
Or consider the famous “marshmallow test” devised by psychologist Walter Mischel and tested out first in his daughter’s elementary school. You can have this marshmallow  right now or, if you are willing to wait, you can have two marshmallows. Some children were able to wait and others were not. My interest in the Marshmallow Test as a way of envisioning heaven is only that heaven is sometimes thought of as a reward for all the things you didn’t get to do here on earth. Picture the sins you are most liable to as “the marshmallow.” You were able to postpone “eating the marshmallow” here on earth, so you get lots more marshmallows as your reward in heaven.
That uses a different kind of connection than the veggie/dessert combination, but it has all the same flaws. All it really does is to substitute not doing something bad (your own marshmallow) for doing something good (the veggies). Not much of an improvement.
Let’s try one more. Imagine that you want to have a very good relationship, say a marriage, and in order to prepare for it, you go through some really bad marriages. This fails the “pay your dues” test because you don’t really learn how to have a good marriage by having bad ones.  It even fails the veggies and dessert test because there is no relationship—except possibly in the mind of a really bad parent—between between enjoying the veggies and enjoying the dessert. Such a dessert is, at best, a reward for doing something that is judged not to be worth doing for its own sake. That is why the marriages and the vegetables are “bad.”
All those notions of heaven fail right at the beginning. They are so clearly misunderstandings that there is not even much incentive to pursue them to the ugly end. But two other notions of heaven are available. Neither of them takes seriously the notion that heaven is a place.
The first imagines that there is such a thing as dessert. It is everything the meal was…and more. There is nothing compensatory about his notion of heaven. Heaven is like the meal, only more so; like the meal, but without the distractions; like a meal, but perfectly prepared. That notion of dessert is what the experience of the meal leads to and surely that is what we want as our notion of heaven.
In the light of that, I took some pleasure in discovering that our word dessert comes from a French expression that means “clearing the table.” The French verb is desservir, literally to “un-serve” the meal. Imagine your death, then, as clearing the table. You had a wonderful meal  but you dirtied a lot of dishes and silverware. Not to mention the sauce you dripped on the tablecloth and the faint wine ring at the far edge of your plate. All those are cleared away. That is the fitting end of that experience. But it isn’t the end of the meal. After the table has been restored, they bring the fruit and cheese or the sweets or whatever they bring and the appropriate and desired end of the meal has arrived.
In this image, the dessert doesn’t compensate for the meal—as the veggie/dessert picture does—but completes it perfectly. I like that image best of the ones so far, particularly in that it features the “clearing the table” metaphor for death. The one difficulty I have with it is that it requires a “place” in too literal a way for me. If heaven is a place, it needs to be, for me, a “place” in another sense.
I’d like to offer “place” in the sense a married couple might use it in saying that after years of misunderstanding and distraction, they have arrived at “a good place.” Place, in this sense, in another way of saying “time.” We have arrived at a good time. Now imagine that this this couple is a metaphor for a Christian notion—I almost said “the Christian notion,” but I caught myself in time—of a spiritual life in union with God.
Paul imagines something very like that. John is explicit about it, as is Jeremiah. This is a oneness not interrupted as it is “here” (during our life) or “now” (during our life). It is that oneness as it can become when we can give ourselves to it fully. Then we can “come to know” as we have been known all this time. 
These are wonderful metaphors and I enjoy them, but I can’t take that ride all the way to the end of the line. The first problem is that while the loving married couple is a good metaphor for the relationship with God, it isn’t a perfect metaphor.
Imagine that the wife is the “God” figure in the marriage, and we want the husband to become more and more “wife-like.” We can say with a straight face that we aspire to be more “Godlike.” But the strain that is clearly apparent in the language of “wife-like” shows that the intimate loving couple is just not good enough.
The second problem for me is that I can’t make any progress in thinking of heaven as a place at all, much less a place we come to deserve because we ate our veggies. For me, the notion that I have come to a good “place” with God, meaning, as in the example above, a good “time of relationship” with God is as far as I am willing to go. It is as far as the leash of my need to understand what I am talking about, will let me go. I am perfectly willing to imagine that in my struggle to know as I have always been known, I have come to a place where my continued physical existence really doesn’t matter all that much. In this picture, I will have lived “the life of the ages” as the Johannine Jesus puts it in John 3 and “the life of the ages” is under God’s care.
When I die, I want the table to be cleared and prepared for the next course. I’ve heard it’s wonderful.
 “Celestial” refers to the skies, or, in the old days to the canopy which we mistake for the skies. We use it more broadly to mean “heavenly” now.
 Not to quibble or anything, but to whom have you paid the dues? If there are actual monetary dues, then there is a treasurer, but ordinarily it is thought of metaphorically and there is no treasurer. There is only the sense that you have done some less attractive and/or less rewarding work and that you have gained something by that experience—possibly a sense of the value of other people’s work or the way the system as a whole functions.
 It was columnist David Brooks who first gave it the name “Marshmallow Test.” In fact, the children were allowed to choose whatever kind of treat they liked best. That’s really the only way the test would work.
 You might learn how to truly appreciate the good one, but you would not learn how to contribute to it.
 There are, I don’t need to tell experienced eaters, all kinds of ways to have a good meal. Some are symbolic, as in lamb and unleavened bread and bitter herbs. Some are purely sensual. Some are exactly what your body needs right at that time. All those, in this metaphor, are “good meals.”
 That is, in fact, the relationship of knowing and being known toward which the verbs in 1 Corinthians 13:12 point us. Then, Paul says, I will know (a future indicative verb) as I have been known (an aorist, a one instance passive verb). I have tried to catch that relationship in my paraphrase.