I met a couple that had been full timing for over two years in a 1970s
Trillium 1300. No toilet, no AC, small bed. They loved it! Met another couple full timing in a Sprinter van conversion. They had been at it for over a year.
If my wife and I were full timing, it would probably be in a fifth wheel. Then again, I don't see it happening. If we were snow birds (stay in one warm spot during the winter months), it would either be a fifth wheel or a park model. We have yet to have found that "special place" where we want to spend all winter. For one or two months, our
Escape 19 works fine.
Really, we have too much stuff to full time in an RV. No interest in eliminating everything, like my workshop, so I can fit in a smaller space.
Friends of mine have a mobile condominium, OK, its actually a 40 foot Class A motorhome with three tip outs. Their mobile condo feels as big as my home (we have a very small house). They even have 1 1/2 bathrooms! With tip outs opposite each other in the living room/kitchen, it makes for a very wide space, very roomy.
It's not camping. But on the other hand, they have their own condo wherever they travel. It's a lot cheaper than owning several condominiums, or even one condo in many places.
Maximum space = either big fifth wheel (think 40 footer with multiple tip outs) or big motorhome. I think motorhomes are limited to a maximum of 45 feet. Just don't plan to pull into many campgrounds, particularly state and national parks.