I used to mothball my bongo over the winter during the frst couple of years of ownership,there were a few reasons for this, the main one being that it wasn't undersealed at the time,and i feared gettig caught on a gritted road,and the simple fact that the bongo was just an MPV back then,and used only very occasionally,so i'd declare it SORN for 6 months,but not forget about it,i'd not go a week without starting her up, running her to full operating temperature,aircon on&off,roof up&down etc etc.
For the storage period i'd inflate the tyres to 60 p.s.i, keep the fuel tank completely brimmed (in an effort to minimize condensation in the tank) work the bongo up and down the box to warm the gearbox,and slightly move her position on the tyres to spread the load over the period.
It didn't seem to cause her any undue stress
And a VERY long drive would ensue as she was put back into commision.(after a full service of course)
That's ruddy expensive 
