I did some new tests with firmware 8.20 for understand impact about some functions.
In particular I test it with and without watchface with or without seconds and heartbeats indications, and I see that there isn't any relevant difference, it fill the same.
I test it too difference from oxygen test all the day and only in the night, and here I see very big difference without change anything other and always in my normal use (with bluetooth, wifi and everything that I use): I go from 3 days and 10 hours to 6 days and 1 hour for 100% of battery drain (I did 3 test for everyone and with battery drain around 70-85%). It's possibile that oxygen sensor is soo relevant about battery? If I turn off in the night too oxygen sensor, I think that I can have 8-9 days for 100% of drain, but what change for data? I have not what? Adapt about clima?