First thing to check is the electrolyte (water) levels in all batteries is at the proper level for all cells. If you have sealed (maintenance free batteries) never mind. Then make sure all batteries are properly charged up.
As far as the engine part of the motorhome, you may want to add the correct amount of fuel stabilizer (readily available in the automotive section at Canadian Tire and such) then make sure you have the gas tank completely filled (to mix the stabilizer and the gas) and to minimize condensation from developing. Remember, the generator uses the same gasoline as the motorhome engine, so you may want to run the genny with the stabilizer/gas mixture.
When you do your monthly testing, start the motorhome, start the genny, turn on as many things as you can electrically to give the genny a good workout for at least a half hour or more each time. DO NOT turn on the televisions during the periods of really cold weather (basically until you're ready to go camping again).
Ken and Terry
2010 Georgetown 330TS being pushed by our
2017 GMC Terrain toad (4 wheels down)