How much is a pressure test really going to help to find water leaks? There are lots of places where air can leak that aren't a problem (requiring repair) like the weep holes at the bottom of windows; around holes through the floor around pipes, ducts and wiring; around the fridge opening; ceiling vents; slideouts; etc. Just curious, maybe I'm missing something...
Water can ingress even in through hairline cracks in a wall or roof membrane that you can't even see sometimes. That's been one known cause of water ingress in buildings and mold and became more commonly known as a result of the "leaky condo crisis" of the 80s.
I would think a close visual inspection would be better along with regular maintenance. I think an RV cover would help somewhat as a preventative measure.