For us, since we sail usually pretty much most of the year, we just roll 'em up (RF jibs, main and mizzen) and ignore the wetness. Of course, our sails are dacron not flax, cotton or hemp, which are subject to degradation from wetness, which dacron is not. However, if one has laminated sails, like tape drive, which are subject to mold between the laminate layers and cannot be removed, it is a problem if left wet for a long time.