Switch to a MIPS transflective or e-paper display as on a Pebble or Garmin, OLED and LCD displays on Apple and Samsung watches look pretty indoors (when they're not turned off to save power) but are hard to read outside (without excessive brightness) and are battery gobblers.
Just charged my Garmin Fenix for the first time in... 9 days (it was down at 18%, could get a few more days but it makes me nervous), most of the battery use went to some 11 hours of GPS activity recording and heart rate recording. Could get 30 days if I turned off the features the Pebble doesn't have.
Even Garmin has largely moved to AMOLED screens. They look great both indoors and outside and with modern technology they are not as battery hungry as they once were. Personally I find the battery life on my Apple Watch more than acceptable. I charge it while I’m showering and getting readying in the morning and have never had any issues even though I am a very heavy watch user and often use it independently of my phone.
I used to have a Pebble Time and agreed the battery life with those displays is nice, but honestly it doesn't bother me to put it on the charger every evening.
The only real benefit a longer battery life would have is not needing to bring a special charger if I go out of town for a few days, but I solved that years ago using a power bank that has qi and watch charging pads on it as my travel charger.
If anything, I'd switch back to a Pebble or similar because the Apple Watch does too much and I don't want that much gizmo on my person all the time. But the Pebble reboot products don't do it for me design-wise.
