I've never bothered with putting jacks underneath, did wind the stablizer legs down though, while you can't use them to jack the vehicle up, I figured that they would help keep the full weight of the van off the tyres even if minimally, before going on another trip or if they looked a little flat, I would check mine from time to time and if they needed air inflate them again.  Usually when I stored the van I would put a bit more air than usual in the tyres and then re-check them before a trip to get the right inflation etc.

With the battery, I kept mine connected but gave it a recharge for a couple of days now and then, also ran the fridge for a couple of days also before de-frosting again (with door open).

Hans, regards A'van campers, some say if storing in the open, it is better to have them erected for better ventilation and heat build up, I always opened my roof vents a fraction whether I had the roof up or down when storing, the raised base of the vent prevented any water from getting in and I never put them up high enough for any driving rain to get in.....