You should definitely bring it inside for the winter. Extreme temperatures, both hot and cold, cause batteries to deteriorate. Your battery's ability to take and hold a charge is negatively impacted by the hot and cold. Best thing for it is to take it inside for the winter. Charge it once, but don't leave it on the tender. Overcharging is bad and most tenders that purport to be "smart" only have a shutoff when the voltage reaches a certain level, which is not reliable as the voltage of a battery varies based on size, brand, chemistry, etc. So charge it at the end of the season, maybe top it off one or two times over the winter, and you'll have a happy battery.