When you park it for any length of time and it's not plugged in, disconnect the battery cables, don't rely on the factory disconnect switches as they don't disconnect everything. There are parasitic loads from the propane and carbon monoxide detectors that aren't shut off by the factory switch. They will eventually drain the batteries.
And no, don't just let the batteries go dead and then recharge them. If you do this, you'll buy a lot of new batteries. If you don't want to take the time to take the battery leads off, then install a read disconnect switch yourself.
Bill