FWIW I purely use my S9B for running, I don’t wear it through the day therefore none of the HR monitoring, notifications etc are enabled. I usually charge mine every 10-14 days and that’s averaging around 70-100km/week of running
On the mountain race I did last weekend I was running for 7hr40 and after I had stopped recording my battery was on 74%. Pretty impressive considering the GPS and everything was set to optimal