We face this on both ends of the country as we split our time about 6 months each. In NH I have the house power on so a battery maintainer is an option. Between the motorcycles, cars, and tractor we need 5 of them. Wallyworld! I don’t disconnect the negative side on the tractor, the 1995 Miata, or the motorcycles but have my son stop and they get a few days on the maintainer each month. 2002 is the most modern vehicle there though. From 2002 the residual draw on batteries must have gotten higher. The van seldom sits for 3 weeks and I can put a charger or maintainer on that. The 4 runner sits all summer in a garage that gets to about 95º and we turn the power off. It gets charged before we leave, the negative side is disconnected, and when I return in 6 months it will start the vehicle. When we now return I have begun putting it on a 6 amp charger for a few hours to assure that. Heat seems worse than cold for battery life as long as the battery doesn't get so discharged it freezes. Trickle chargers work and if you can mount the connections for one preeminently to the battery or to the charging posts there is a small SAE plug that can be under the hood or zip tied to the grill facilitating connection. Deep discharge kills FLA and AGM batteries, everybody knows that, as they say.