Welcome! I guess it depends on your style and frequency of camping. Do you go out just a few weekends during a 4 month summer season, or are you planning to travel all over the country for 6 months at a time? IMHO you camping style will effect how much room you need. If you are away from home for long periods of time you may want your own on-board washer and dryer, extra clothing for changing temps, more food storage space.
As full timers we find that our 44' toy hauler fiver is about the right size. There is no way we could survive without a king bed, 1 and 1/2 baths, and a washer and dryer. For a regular fiver (non toy hauler) you can find about the same floor plan options I mentioned in a 39' or 40' model.