A watch that needs charging every 18 hours sounds utterly awful.
Didn't Apple watches always need daily charging? Not a real problem for me as I take my watch off at night.
Indeed, you just routinely charge it every night, much as you do a smartphone. Come the apocalypse, of course, I anticipate issues with the global power supply, so I won't know what time it is, which will be annoying considering the endless night. A bit of shame too, I figure being chased by demons is a workout worth recording. Anyway, the battery has never run out in daily use, and that's including day-long hikes with heart-rate monitoring.
I'm not sure the benefits of an always-on display, it wakes up when you look at it. But as said, it's merely incremental now. My watch gets used for telling the time, figuring out when it gets dark (bike lights!), time zones, activity tracking, checking the weather, and getting emails and messages on the move, checking when the next bus is due, contactless payments, and jibbering with music (either from the watch or phone). It's one of those things that I didn't think I needed but since I got one, I do.
Apple do a decent job of supporting old devices, all said. My Macbook Air c2011 only went out of OS updates last year, which isn't an unreasonable lifespan.