I used to work for an auto parts dealer in the cities, i talked to a rep. from exide about care for your batteries. He said they have done testing on old wives tales, He said there is no need to store your battery on wood, the reason that the tale started was in the 1920’s and 30’s the batteries were made out of wood, and the coldness from the cement and ground would draw the amps out of the battery. now days the batteries are made out of plastic and they hold the amps in better. To your question, waterfowler is right, if the battery is fully charged it will not make a diffrence, when spring comes make sure the battery is fully charged at 12.6 volts or 14.6 while the boat is running. sometimes you might have to recharge it for a couple of hours. one more point, keep your battery clean, the dirt and the oils on top of the battery carrys current from positive to negitive terminals causing a slow dicharge in the battery.
thats my two cents!
thanks!
bart