Think the main problems are, flat spots on the tyres, moisture in particular and a flat battery.
Solutions: axel stands to take pressure off the tyres, All weather breathable cover? for the moisture problem, take battery out and hook it up to a trickle charger at home.
Hope this helps.

I had my S1 standing for about 2 months, kept it on charge, wheeled it back and forth everyweek and the garage is dry so it was fine and started first time with a roar