I'm surprised that when you turn your gas off that your lines empty so much that they need extensive purging when you turn them back on.
My old 1990 Winnebago Warrior has a pressure gauge built into the system. I access it by taking off the access cover on the outside of the RV for the refrigerator. It has two needles. One measures the pressure in the propane line, and the other is a manual "witness" indicator. You turn on the propane, then manually dial the witness indicator to match the pressure indicator, then turn off the propane. Check on it in a couple of hours. The two needles should still be lined up together. If the pressure has dropped, it will no longer match the witness indicator. This means that you have a leak in your system and it is not holding pressure.
I turn off my propane at the tank every time I am done using the RV and put it back in storage. If it has been a while since it was last used, sometimes, but rarely, I have to turn on a burner on the stove and let it run for a few seconds before it will light with a lighter. It is at the end of the run for my RV so if the stove runs everything else should have gas also. Most of the time though everything lights up without effort because my system does not leak.
Steve