I've also thought about songs and books my characters would like, which make me think about why they'd like them. This gives me more of an insight as to their tastes and why my characters have these. I sometimes interview my characters - again it makes me think more deeply about them and I hope future writing about them will show some of that depth. All of these things make for posts for both of my websites, of course, but it all feeds back into future stories.
So I would urge any fiction writer to fill in the details. You might put them on a blog and/or website or keep these entirely to yourself but you will understand your characters better and as a result your stories will be stronger.