The challenge, at least for those that want to use the watch for sports, is not the "daily" use, but that the watch runs out of juice so quickly when using its location tracking, aka GPS sucks battery.

So, the reason that I want longer battery life is not, per se, to charge once a week, but so that I can use it on a longer run, and not be afraid that the battery will give out as I get close to the finish line.

Without any special preparation my apple watch will last a full day of hiking while recording the GPS/heart rate/etc. (i.e. 5-7 hours hikes in the mountains.)

Cellular, on the other hand, can drain the watch relatively quickly. Mine lasts 2-3 hours when streaming music from the cloud and relaying to bluetooth headphones during a workout (i.e. when it can't piggy-back off the phone's cellular.)

would be nice to reverse-charge from phone to watch - is this possible?

The S10-line from Samsung has that feature so it's certainly not impossible

There was speculation when the 8/X came out that they would have that feature. I would love it. Too many times, I have forgotten to charge my watch in the morning and only remember when I go to to run errands and see it in red. It’s not like you can just plug it into a lightning cable in the car and top off. I refuse to get a watch charger just for the car.

That's not possible (and probably ill advised as the watch will usually outlast the phone) - however it is possible to charge your devices from an iPad.

My issue is that I wear it overnight and through the day. And what happens is that around an hour before bedtime, the battery gets to 20-30% but since I'm not constantly checking, I forget about that and don't take it off my wrist to charge it.

The only low battery notification I get is at like 10%. It'd be handy (heh) at least if we could get better notification reminders that align with our schedules to know when exactly to charge the watch so there's enough power for a night of sleep.

My Apple watch pops a notification to "charge before bedtime" if it's going to die while I'm asleep. Does yours not? Maybe it only does it if you have the sleep features enabled?

That's odd, I definitely have the sleep features enabled and it's a Series 6.

There is an option in the Watch app on the phone (what?). Look under Sleep for “charging reminders”. It will give you a reminder on your phone just before bedtime and you can use that time to charge it up before sleep tracking. It gives you the reminder no matter what charge level it is at.

Mine definitely only gives the reminder if it actually needs to be charged. I don't get the reminder if it doesn't.

Another downside to wearing at night and charging during the day - automatic updates don't happen automatically.

I charge it when I shower and get ready to go to bed, then put it back on to wear overnight because I like the sleep tracking. Never runs out of power.