These days I convert everything to epub *and* prc/mobi.
(Plus I archive the original, of course.
)
When I eventually get organized for real, in a year or ten, I'll add lit to the mix. I'm not sure its really dead.
I'm not ready to buy into the eub-only bandwagon just yet; the way epub is trending, with warring DRMs, I expect to see other "universal" formats appear before long.