My Apple Watch ( Series 1 ) is still alive and working quite well. It lasts for 8-9 hours if I don't use the heart rate monitor, while doing sports. I think at this point I could say that my Apple Watch is not "all-day" battery life.
I would assume sleep tracking would never be a feature. You need to charge your Apple Watch every night, so that's off the limit. I use Fitbit Flex 2 to track my sleep and I wear them both during the day, however during the night only Flex 2 stays on one of my wrists.
Unfortunately Fitbit decided to discontinue the display-less flex 2 and now I'm a bit confused on what to do next.