Which statistics show the average American living to be 90?
Also, you’re unsure of the medical expenses, but give such specific numbers for the travel, food and RV? Please explain how you came to those numbers.
Merely trying to be optimistic and helpful to the OP who literally provided almost nothing to go on. Average life expectancy is 77, but RVing reduces his risk in nearly all of the major categories of leading causes of death (heart disease, cancer, CV19, accidents, diabetes, respiratory illnesses, falls off ladders.) One might argue that being on the road increases car accident likelihood but in a huge RV I think survivability would be quite high.
Retiring at 55, prime of life, dropping most of life's stress behind, to go have an enjoyable RV life. No work stress or meetings and schedules, plenty of sleep, plenty of fresh air, presumably walking through parks getting exercise and maintaining a happy positive attitude! Considering heart attacks, lung diseases, and diabetes are the major killers, I'd say such a life would increase the typical person's life expectancy provided he gets exercise walking around national parks and watching diet, eliminating stress, plenty of fresh air.
Doing these activities, presumably means he's also not doing very risky activities, criminal stuff, drugs, heavy drinking, hanging out in bars and casinos like so many retirees, or sitting on the couch awaiting death without purpose. He won't be at home on a ladder or on the icy roof with Christmas ornaments or using a chainsaw to cut back the tree limbs, not sitting on the couch sucking down Rum and Cokes, etc. Now, if he said he was going to retire at 55 and sit in Vegas Casinos as his hobby, I'd have a different analysis.
I'm also optimistic that medical science will add probably a few years to life expectancy in the next several decades. LOL, I've put more work into my answer, than the OP put into his question or that you've put into any answer.
Sorry if my post in some way ruffled your feathers, although I cannot for the life of me understand why it possibly could. I'll try to be more careful. Next time, I'll spend a 1/2 day doing amortization, medical, and financial planning proposals for the OP, complete with 3-team presentation slideshow and binder handouts, to within a few dollars, that he'll need on his RV retirement adventures.