If it's been winterized, and your storage is in the high desert of Oregon, I think the best thing would be to open closets and cabinets and leave it go to natural temperatures. We leave a roof vent cracked open a bit (with a vent cover) and open a window 1/4" (with a cut to length wood block) to allow air in and out. Heating it will only make it nice for critters, 4 and 6 legged ones.
Bob & Donna
'98 Gulf Stream Sun Voyager DP being pushed by a '00 Beetle TDI