Its a bit of a funny thing really. In a way I could pretty much get away with just one character slot - The Stamp. It seems to me that this is the way most people probably play anyway... they have one main character.
If the other slots are used its generally because we got bored, or wanted to try something different. But I reckon if I added up ALL the time I had spent with my other characters it would still be less than the time I spent with The Stamp.

Don't get me wrong, I apprecaite the other character slots, and I think currently they are all full. But in a way its a bit like the last half of the block of choclate, really I'm just eating it 'cause its there.
So, what about you guys? Could you get away with just one character slot? Or what about if you had half? Only 4 slots, who would you keep, who would you kick? Have you ever deleted a character that was over level 12... or level 20???