I get approximately 24-30 hours between charges on my Watch. The best I've ever done was around 38 hours, but that was when my watch got down to about 1%!
I use my XR a lot throughout the day, so I usually end up with 30-40% battery by the end of the day. On weekends, I use my phone less, so more like 70% at the end of the day. My Apple Watch 4 usually has 70% at the end of the day.