I have mine marked 1,2,3, like old man Mavic does. Keep them in rotation, fly at least once a week. I always use them from left to right. The last one used is inside a safety case, every body develops their own system, what ever works for them, so, right now have #1 in a fire proof case, #2, I just used, sitting next to my drone with 25% charge. So, that tells me #3 is next to charge up, and if want to fly longer I charge up #1. Works for me, like I said, what ever works for you. Important thing is to rotate the batteries, and, to keep my women happy, I always keep battery in a safe fire proof place.