An actual gas leak could be caused by a number of conditions. I had one with the valve on the tank which had a leaky stem gasket so that when you turned it on or off, it leaked. It didn't leak in the fully off or on position but if I were to leave it half open it would.
I had another leak in the hose that connects the tank to the regulator. It was actually a leak where the flex hose terminates in a fitting.
My preventive is that when I fill the LP tank, I have the tech soap the hoses, valves and the tank area in general. I do that every time. Then once a year I take it to a RV shop where they do a test on the system. That involves putting a gauge at some point in the LP plumbing, take a reading (with the main tank valve open) and let it sit for 4-6 hours. Then they read the gauge again to make sure the initial reading hasn't dropped.
On my RV I only have LP hoses at the regulator. From that point everything is hard metal pipe throughout the RV. Someone else indicated in a past forum post that their RV had a network of soft hoses and recommended that they be inspected/replaced at regular intervals.