If this is your motor home and you've owned it for 7 years, YOU know more about it than anyone else in the world! If all your appliances, and equipment is working well right now, they why try to fix something that's not broken. An inspection (in my opinion) would be a waste of money.
On the other hand, if you are wanting to sell it and you want some kind of documentation that the RV is in sound condition to leverage a stronger selling point, then go ahead. But selling RV's, just like cars, an inspection on the part of the seller as some kind as proof the vehicle is sound, is not any better than the paper the report is written on. I would be even more cautious if the seller produced a paper that stated the condition of everything. I would think the paper was bogus and the seller was giving me a snow-job.
If you are planning on keeping the RV for as long as possible, then deal with issues on the RV as they occur. If you already have multiple issues and you find it next to impossible to put the money into the RV to fix everything, then sell it as is and let the buyer beware.
Not knowing what you want the inspection for, it's hard to say if it's really worth it. But if you want peace of mind ... you own mind is he best judge! You don't need an inspection if everything is working OK.