Last Monday Apple released the first software update for the new version of WatchOS (version 9.1). The big thing that was promised was an improved Low-Power mode for the ultra giving it at least 60 hours of continuous use.
Of course, I had to test it. Wednesday morning I put it on my wrist and kept my normal usage pattern. This includes using it to track sleep, taking a 30 minute walk each day, handling mail, reviewing calendar, playing some podcasts and using it to track my sleep.
When I finally took it off on Friday evening, I was down to 12% battery. Not bad for 63 hours of continuous use. I think they may have something here.