Deciding when to buy a motor home?

A lot of your comments have been very helpful. I would like to clarify my question regarding the amount of trips or miles driven. When I owned the airplane, the rule was you needed to fly at least 100 hours per year. This is because less means the airplane is sitting to long. So I am looking for a similar rule.

Also regarding the Thor, looking at a used 2014 version. Wife likes the size as she feels can handle it, also like the layout and the king size bed. So I would like to here about any issues regarding the models either Axis or Vegas. Good and bad.