I am also using the series 5, battery life more or less feels like the same for me. I am ending the day at roughly 30-40% battery life.I installed the watchOS 10 RC last week and apparently it's the same as the final version. I own an AppleWatch Series 5 and so far I was perfectly happy with it, after a full day at the office I easily had 25%ish left of battery life. I would say it lasted up to 16hrs.
But now, with watchOS 10 my battery life is down to less than 12hrs. What is your exeprience? I hoped that they would fix it with the final release, but they haven't.