Vehicles really do not like sitting for long periods epically in the sun.. On a motor home many things can go wrong, ON a trailer, the major complainers are tires and wheel bearings...Which is why I tell folks if you are going to park it and leave it for a long time, go with a trailer.
UV-Light is the killer on tires, and many wheel covers do not do a decent job of blocking it.... I used to have an electronic "Pig" that was designed to be sat on the shelf on a fridge and oink at you when you opened the door and it saw the light.. It would OINK when covered by many tire covers cause it still saw the light. (Foil blocked it)
Thus I too recommend a plywood cover and a cloth cover (For appearance) over that.. I do have cloth/plastic covers for my rig, they come in very handy when I use them as projection screens for my Mr. Christmas Projectors.
RE-pack wheel bearings (if they are the packable kind) before you leave, and inspect the tires to see if they need replacement. that is the only special instructions I will add. Depending on how long you leave it, Covering wheels, getting them off ground, all that may or may not matter, Leave it long enough, and it wont matter you gonna need new rubber. Hence the inspection.