Assume that there is a heaven, and assume that most decent people go there when they die, like in the movie Ghost. Say you're Demi Moore and your love for your dead boyfriend has just been validated because he re-appeared to you after killing your potential murderer and then ascended to heaven. So there you are, certain that the man you love is dead, is no longer with you, just went to heaven. Furthermore, you're pretty certain that you're going to go there, because, you know, you don't covet your neighbor's wife or eat too much or anything like that. So what do you do? How do you live the rest of your life? Alone? Because you know that if you find another lover, and he goes to heaven as well, then when you get up there, there are going to be two guys who love you and they don't know each other and then what have you got?
Therefore, heaven is either a big faceless orgy, or we're already in heaven and when you die, that's it, because it would just be too complicated otherwise. Which isn't a huge loss, because how great can heaven be if you can't have sex there unless you're married? Is the main appeal of heaven the fact that there are no demons torturing you regularly and the central air works? Because I'd take no afterlife to the prospect of that one. Basically, how could heaven be any better than life here on Earth, for better or worse? Why not act as though we're already there?
Therefore we should all have more orgies. You only get one chance.