onagar makes the interesting point that a lot of us who don't believe would quite like there to be an afterlife. And yet we still can't believe in it. Its not something we don't want to happen - far from it.
And yet, no matter how much we might want it, we can't assume there is one when there's not a scrap of evidence. I mean, it's like somebody telling you about the best holiday resort they've ever been to, and not having photos or being able to locate it on the map.
It would be great, actually. I'm thinking of all the time I'd have to get all those books read and box-sets of old TV shows watched. Assuming we were allowed to do what we wanted, of course. I rather get the idea that, in the Christian idea of heaven, a lot of the things I'd like to spend eternity doing might be banned (eating and drinking, watching Doctor Who, partying with Girls Aloud, when they finally got round to having the decency to join me up there... (imagine me looking down and going "more drugs, Sarah, more drugs! You're needed! Don't forget to repent at the door or the bloke with wings will send you in the Down lift.") (*)
If there were an Eternity I'd probably want to spend the first few hundred years or so just browsing the library. Then I'd start making up the list of dead celebrities I wanted to shag meet.
(*)In fact I'm actually convinced most of the interesting people would be down in the Other Place, where all the best parties would be happening.