I will say it wasn't great when I had the non-Ultra. It was fine at first, the watch would last a full day, but like 2 or 3 years later it would struggle if I did a lot of exercise in a day to make it to the time I go to bed.
I also recently went on a 5-day backpacking trip and it was a struggle to keep my phone and watch charged with an external battery. If the ultra lasted even 3 days instead of just 2ish on a charge this would have made it way easier. By the end of the trip to save charge I just gave up charging the watch.
But I agree there is a huge difference between once-daily charging and once-weekly charging.
You can't just throw it on the charger for a few minutes before bed and awhile during shower in the morning?
That is a big deal to me personally, that's an extra routine I have to incorporate into my day that given the option I'd rather not.