Do not listen to the dealer. Let me give you and example. In my motorhome, I have three batteries. 1 12volt for the main and 2 6volt for the coach. I do have a shut off switch for the batteries. The one for the 6 Volts is ran off the main battery. Then I have a manual switch for the for the main. My motorhome is completely dead now. After about 3 or 4 months later, I go to get it ready for a trip. I turn on the main battery and then the switch for the coach batteries. Nothing happens. The batteries are completely dead. They were so dead that they would not hold a charge and I had to buy neww batteries all the way around. Get the trickle charger. Keep your boat batteries on them until it is used again. My boat is in the garage and on the charger right now. We came back from our last trip about 2 months ago. I forgot to put the trickle charger on the batteries. It took about a day and a half to bring them up to fully charge. The charger was off for about two months with the Perko switch off.

Now in regards to the motorhome, I had the dealer install a solar panel on the roof. I will never run out of juice now.