My vessel had been on the hard for several years before I found it, and there was damage that would have been prevented had it been covered. I think covering your boat is one of the best preventive actions you can take, and I am another owner who is a big fan of shrink wrap. The zippered door in a wrapped boat gives access when you want to check on things or work on things, and adequate vents will keep it from turning into a sweat box.
I sleep on board before and after launch and recovery, and use the toilets in the facility. Water tanks that are accessible can be emptied to "dry" with a water vac and a pet wand, something I do every year to winterize.
Another two cents for your consideration :-)