I bought a lightly used Apple Ultra Watch 2 6 months ago and it solved all my issues with my previous Apple Watch - specifically battery life.
I can use it as a sleep tracker and only need to charge it once every 2 days unless I take extensive hikes or use a lot of camera remote control.
The latter is magical btw especially for solo travelers - ability to set a scene on the iPhone camera while being in it by glancing on your watch is science fiction!