Engine starting battery being charged while parked?

Ours has a battery shut off switch so nothing is drawing from the engine battery when parked. We usually leave it on though so we can start the generator from inside if we wish. We have not had any problems with it discharging while sitting, but we are parked in a warmer climate during the winter. We also have a shut off for the house batteries so could also use that and shut all batteries off if it were being stored.