The only limitation is you have to be outside during the day with the watch exposed a few hours a month or cheat with other light sources.

You really don’t. Maybe other watches use more power but I left my gshock in a drawer for months, maybe even a year and when I took it out the battery was at “M.” Put it on a window sill and it was at H in no time. Haven’t actually seen it in years and I wouldn’t be surprised if it was still alive.