I have gone up to 45' and had everything in between.Large trailers/fifth wheels are great for RV park type setting and very poor at off road boon docking,at least here in Idaho.Going through any dip getting off road usually drags the rear end of the unit and making it a round sharp curves is problematic.
For my use I have found 30ft tongue to bumper the absolute longest I should have to get into those hunting and fishing spots off grid.Actually,24' is much better and smaller is better yet but the 30' I have makes the wife and dogs happy with all the room and it works for 99% of the places I want to get to.
If I was going to be a pavement queen and just hit RV parks,larger is better with more room being more like home.Larger units do not fit in a lot of Forest Service campgrounds around here....
Camping is camping..I spent many a night on the floor of my parents trailer when it was cold and snowing out and if it was warmer,I was always in a tent with the rest of the siblings.