Very possibly running on borrowed time and a lot of luck without a pressure regulator....strongly suggest you make the minimal investment.
We don't usually shut off the water overnight during the spring/summer season. However, when the temps in the fall start getting toward the lower 30's we do. We try to remember to shut if off whenever we leave the area of our campsite, but sometimes "old" people forget...which seems to be happening more often lately. A good practice to get into.
One thing we did learn from some old camping buddies is that the very first thing I do after hooking up the water and turning it on is to go inside and double check none of the faucets have been left in the open position. One of their first trips with their HTT, they were with family in another trailer, unhooked, plugged in, hooked up the water and spent some time outside chatting.....until they saw water running out from under the trailer. Somehow, the faucet in the bathroom had been left in the open position and the stopper was in, so when the sink filled and filled.....not a good thing, so that is #1 after hookup.