That's 36 hours of normal use, with a 60 minute workout[1]. My Fenix 6 lasts 8 days of normal use and currently tells me it can record a 14 hour run even with only 42% battery.
[1] - Details in footnote #1 on https://www.apple.com/apple-watch-ultra/
[1] - Details in footnote #1 on https://www.apple.com/apple-watch-ultra/
And if one could ever get a cellular enabled watch without an iPhone, I'll be first in line.