My dad and I both store our trailers in my shop. He likes to use the disconnect switch and then put a battery charger on the batteries, it keeps them topped off. I don't use the disconnect switch, but instead just connect to shore power and let the intelligent converter maintain the batteries.
It does not seem to matter which way, both work. I would have some sort of charging plan to keep battery from dropping too low, whether that is periodic charging or trickle charger or ?? but two things will kill a battery fast, letting it get discharged too much and over charging/boiling (ok, there are more than two, but those are my top two issues).