When I had my shop, one income stream was that of storing bikes in winter (Thanksgiving break to Spring Break, usually) for the many college kids in the town. Our storage facility was a war-surplus quonset hut (60 feet long!) with just 2 windows and 2 front doors (which entered the back of my shop). We stored hundreds of bikes in there, uncovered with batteries removed (those went to a charger rack where we maintained them for the winter, charging once each month for 4 hours, every battery). No bike failed to start easily the next year, and they only got a little dusty, no rust nor corrosion, even on the dirt bikes.