Where I keep my boat for 5 months there is no electric. So I have a battery maintainer connected from last boat run(early October) until it goes to sleep mid November. Then just turn the battery switch off. BTW... a trickle charger will cook the batteries, maintainer will not!

I leave mine in the boat with the switch off. Spring time throw them on a battery tender. Never have a problem. I have 2 Interstate 1000 CCA , I think they are like 5 years old.