My unit is sitting on a concrete pad so I have one side leveled with legos and the other tires are sitting roofing shingles (one layer). At this park they do not authorize anyone to put their units on blocks. They want the units to be able to be mobile if for some reason they need the trailer moved. Even though are permanent spots here, they don't want them on blocks or have permanent patio awnings unless they can slide out and detach from the unit. I have my tires covered but I do agree with the 5 year mark. The trailer I had before had new tires put on in 2000 and I traded it in earlier this year but tread was good and i had no problems with them. But regardless the tires would have needed replaced if I kept it cause you just don't know how bad the inside is deteriorating. Many folks cover their A/C which I have one of mine covered, because I plan on using the other A/C (heat strip) this winter for some circulation in the bedroom. Also, most folks treat their rubber roof with UV protection and conditioning, or a least clean it really good before the winter sits in and may wax or wipe the exterior down with UV protection like 303 Protectant. Windows you can use Frost King clear stretchable plastic, which I bought but haven't installed it yet ;-( (but i will soon). Another thing I plan to do is attach a PVC pipe to sewer line and get some heat tape and pipe insulation for the water hose, and seal any holes with expandable spray foam insulation and I will be ready for the winter (I hope)
Good Luck to you! Allison