I have a SSSB (SBSS?) series 0 since July 2015. Daily wearer, daily workouts (walks, elliptical, other), frequent texts, mostly the same watch face. Zero third party apps are used. I check weather, use the timer, and calendar (for notifications).
I have screen burn noticeable on the image watch face. My battery life is ok (lunchtime recharges get me through most days). Charge every night and I wear it for 16-18 hours per day.
I wish I stuck with WatchOS 2.x.x and never upgraded past it into 3.x and 4.x. That was my favorite.
Siri craps out (no connection even though phone has it), pauses (I’ll tap you when I’m ready), and some actions seem to take forever (tap to reply and wait forever for the screen to update). It’s less snappy. It stutters. I’ve reduced heart rate accuracy/frequency during workouts and trimmed some other features to improve battery life.
Planning on upgrading to an alumininium black and using the zero for dirty work like working on the car where it can get damaged. Stunt watch from watch4 on out. The black link band is wearing on a few links. I think I can swap in spaces to look new again.
Expect to get 3-4 years at best. After that, I think any watch, no matter how great it is, will start to see battery degradation.