We have a 34 ft rig and have found issues at some forest service and state campgrounds without any length restrictions. Mostly because the roads are narrow for today's wider rigs and the trees are encroaching the roads and sites.
At some sites the trees are only cut up to about 8 ft, which means our 13 ft tall gasser gets scratched or we park on the far side to try to avoid it. And it is very site specific; there is no way to know in advance if the site you reserved is going to have a problem or not.
The other thing I've seen a lot of in Alaska is that the park may say they have sites that are over 40' or unlimited length, but unless you can reserve one, which often you can't reserve, you may find that the truck campers and small trailers have gotten them first, and none left are big enough for the 40 footer.
If you stay at private parks, you won't have this problem, they will reserve one for you that fits. But still may find tight manovering. Some people are amazing good at getting in these tight sites.
The smaller you are, the more flexibility you have. But still for full timing, it seems the space needs would likely override that.