LP regulators last almost forever, at least 3 to 4 years or more. I rarely have to replace LP regulators and I am a tech at a large RV service center. I do have to replace the feed pigtails from the tanks to the auto switchover because THEY will leak at the hose crimps. Do the regulators fail and leak or you just "think" they are bad due to your Precision Temp water heater and your stove? If so, that is a BAD way to determine your LP regulator is bad. You need to have the LP pressure checked when you have appliances running and when no appliances running. LP regulators ARE adjustable if the pressure is not correct. If I were you, I would get rid of the On Demand and get a regular 120/LP water heater. On Demand RV water heaters are ALL problematic and as you found out, very finicky on operation. When you state the stove does not light on the first 2 try's. You mean the range top burners and you are turning the manual piezo knob to light? If so, THAT is normal. It can take multiple clicks on the Piezo to light range top burners. Doug