Other things will make a difference also. If you go to some cheaper places or little county parks or bare minimum spots they will often times have anything from a plastic pota jon to a very nice rest room. You dont have to use the rest rooms all the time but it saves your black tank capacity. Some might be only $10.00 and limit you to 14 days or so and have a dump station, rest rooms, showers, and a water faucet. With those conditions it's easy to stay put for two weeks then dump and move on. Worst case you may have to walk a few buckets of gray water over to the dump.
I have been in areas that let you dig 6 inches deep and bury black and gray but x number of feet from lakes and streams.
Wife doesn't use the rest rooms that much because she has a hard time squatting while both feet are up on the toilet seat.