Same problem here only had this watch 3 months. Frontier S3. Updated Monday night and left on charge till Tuesday morning by 12pm Tuesday is was down to 45% and dead by 3pm the watch normally lasts me 3-4 days. This is a disaster Samsung it needs fixing asap.
My watch showed 100% despite already 1 hour usage. Will see how the day goes
UPDATE: after 10 hours plus, I still hve 72% left. For, this is quite normal for me as my watch usually can last 2 to 3 days.