I bought an Arrow a while back that had been stored outdoors up in
Ottawa for 5 years. The owner had purchased a full set of Kennon
covers for cabin, cowl, wings, and elevators as well as insulated prop
and cowl covers for winter preheats. That left everything covered
except for the back 8 feet of the fuselage. That last 8 feet shows
noticeably more dulling of the paint, and the covered areas still look
great, so the covers definitely help. There is a little chafing of the
windows in the wind, but not bad.

I now use a hangar, but it leaks as many do, and the plane gets very
dusty, so I think outdoor storage isn't so horrible. The main problem
is getting preheat in the winter out on a pad if there's no power
outlet anywhere nearby.