My Mavic Pro batteries are 4 years old and they're still in excellent condition, but that's because I set them to auto discharge to storage voltage after 1 day of inactivity. I must say the Mini 2 is an incredible piece of engineering and miniaturization. It's so small and light. I think the battery itself is heavier than the drone without battery.
since the Mavic Pro, we still have this? I think they should start lowering the max charge of the batteries. this is ridiculous. I have one battery that refuses to charge, probably unbalanced, then in 1-2 years, bloated.
If you're not flying your drone for a while ( a few days or more) I would take the battery out (don't leave it in the drone). I top mine off every few weeks to make sure they are (mostly) charged and to maintain them. I think people forget that if you don't use something for a while, you should take the batteries out and charge the batteries at least once a month as they will lose charge on their own from sitting. This also applies to cameras and other electronics.
A typical 6-volt golf cart battery will store about 1 kilowatt-hour of useful energy (6 volt X 220 amp-hr X 80% discharge = 1056 watt-hours). Since this would only power two 50-watt incandescent lamps for 10 hours (2 X 50 X 10 = 1000 watt-hours), your alternative energy system will most likely require wiring several batteries together to create a battery bank. Since each golf cart battery weighs almost 65 pounds, there are weight considerations as well as battery gas venting issues to think about.