My Hypalon Avon 260 with air floor is left on the foredeck of my Hunter 356, upside down. It has been that way since 2004 after I bought it at the Miami Boat show. It still is going strong but is showing signs of aging. My rubrail comes unglued in spots as it deflates with the cold air and I reglue it each spring. It is hard to get a good glue job due to the old glue underneath the rail cannot fully be removed. I also have some wear on the bottom from use, but I have not had to patch any spots on it yet. For a,couple of years I had a cover, but it was a pain to deal with, so I quit using it. I have repainted the wood transom as it gets scratched up putting the motor on and off. It needs a paint job now, so next spring I'll do it again.
I put Aerospace 303 on it last spring and it helped the looks. I'm not sure how many seasons it still can go, but think it has a few left. When cruising, I take it off and tow it so I have better visibility from the helm and cockpit.
I don't know how to best store a dinghy. They are bulky, hard to deal with and when not in the boat, seem to just take up a lot of room. If not on the boat, then they don't get used. This one has been used and sitting in the sun. Perhaps this will give you an insight into what your possibilities are when it is left exposed to the sun. We are on the T Nasser River at Kentucky Lake, but spent one winter coming and going to SW Florida.