There are several "ideal" ways of winter storing, completely draining down and leaving taps open, making sure the van is clean of all traces of food and removal of bottles of any liquid, fridge door open, all cupboards open, then either clamping the wheels or raising the van on axle stands to allow the axle to rest and handbrake off.
However, many people do not do it all but leaving the handbrake off is sensible as the brake shoes can, and do, stick to the drums making moving the van next time a problem, sometimes an easy thing to overcome but quite often needing a strip down of the drum.