Battery concerns ...

[Aniseedvan]

I have a 38mm and that's used reasonably heavily and regularly hit <20% at the end of a day. I have tiny wrists otherwise I would go for the 42mm as it appears a good part of the time when people state 50% left at the end of a day it's a 42mm.

 

[stonefeet]

Unless I'm out for a 3 hour ride I'm at about 50% every night on any version of watchOS

The ride alone using Runkeeper uses about 40% battery

42mm

 

[Bob190]

I wear my watch 22.5 hours a day and charge it 1.5 hours each day. Each day includes a run or ride of 1 - 3 hours and sleep tracking at night. You are going to have to charge it each day just like your phone. It's not a big deal to drop it on the charger. I charge mine while getting ready for work in the morning and sometimes before bed.

I don't expect that to change with my Series 2 watch. Don't stress about the battery .. it's a renewable resource.