Just replaced my Gear S3 battery (24$ + 10$ for tools). Excited to get 3+ days back. Links in comments, will report back with new battery life in a few days. : r/GearS3
Samsung Gear S3 update brings battery life improvement - SamMobile
How to Fix a Gear S3 Battery Drain
Samsung Gear S3 receives another update that's meant to improve battery life - GSMArena.com news