The low flame must be pretty healthy in order to keep the refrigerant good and hot. Otherwise, it would take a long time to begin cooling each time the thermostat calls for high flame. In the winter, you may find that the low flame is all that is required.
The refrigerator uses very little propane. So far, I have used just a bit over one 30# tank starting in October. That includes a lot of refrigerator use, a little furnace use, a lot of cooking including using the oven, and the overnight burn-in that the dealer did to prevent smoke alarms from the furnace.
The water heater can be a big user. I always leave it on 120v only except when both of us wnt to shower. Then, I turn on the propane for faster recovery.
John W. Irwin
2005 Classic 28 "Sabre-Dog III"
2013 Silverado 2500HD Duramax/Allison LTZ
WBCCI #9632, TAC TX-10