All the "use/store" switch does is remove many, but not all of the loads from the battery. In many Airstreams, the propane leak detector and the sub-woofer stay powered up. They will run your battery down in a month or so. What many have done is either install a real mechanical battery disconnect switch in the battery positive lead, or actually pull the batteries and take them home, with a "battery Tender" or similar maintenance charger to take care of the batteries.
The other issue is that on some newer Airstreams, putting the switch is "store" still leaves the convertor/battery charger connected to the batteries. If you are continuously plugged in to shore power, this can overcharge and mess up the batteries.
The way I dealt with this was to install a good quality solar charging system, with temperature compensation, and park my AS where it gets enough sun to keep the batteries properly charged.
Battery maintenance is not real hard, but takes regular attention during storage to make sure the batteries stay properly charged, and in the case of "flooded" or conventional lead-acid batteries, that the water level is correct.
Look around the forums for a lot more data on battery care and feeding...
The 2018 Airstreams may have a better battery charger. Mine is a 2007, and the older OEM battery charger is, frankly, cheap crap. A new, and much better one is waiting for me to find time to install it, along with a positive manual battery disconnect.
Rich, KE4GNK/AE, Overkill Engineering Dept.
'The Silver HamShack' ('07 International 22FB CCD 75th Anniversary)
Multiple Yaesu Ham Radios inside and many antennae sprouting from roof, ProPride hitch, Prodigy P2 controller.
2012 shortbed CrewMax 4x4 Toyota Tacoma TV with more antennae on it.