I have been wearing Oura for 4 years now. Unfortunately, they went to a subscription model so that is annoying, but I still recommend them. I have worn it in the sauna, and it doesn't overheat. Fun experiment to pair it with a CGM in the sauna. I have worn it in the ocean. I have lifted weights with it.
They have been solid as far as support: grandfathered me in to lifetime access, warrantied my ring when they didn't have to. They did recently go to more AI support, but I complained and someone quickly emailed me, like they used to.
They are constantly fueling R&D with new features, most recently, 24/7 HR. Battery life is pretty good. They give you a notif at 20% so you don't beat the battery down. I have to charge it every ~4 days, but I have had this current one for ~2 years.
BF 30% off ends today, I believe.