The power consumption on modern red dots is minimal. Just turn it on at the start of the day and turn it off when you get back to the lodge/home/camp. The battery will normally last a few years but I recommend a fresh battery every year. Do it on a specific date so you don't forget.

Note: some red dot sights (like the Burris FF) have an auto-off feature after a set number of hours. If this is the case with your particular sight, then turn off and turn on a couple of times during the day to keep it "awake".