I had the pebble time steel which had a 10 day battery, and interestingly I felt like it was always going flat on me mid day because I'd get the charge warning away from home and forget about it causing it to go flat. While my current 1.5 day watch has never gone flat on me because I put it on the charger every night. I have a feeling this is a big part of why phones and accessories have not moved past the daily charge schedule.
Amazfit Bip and Bip Lite (the latter is preferable unless you need standalone GPS) consistently does 22-23 days of battery life (8-10 days if you use a watch face with seconds).