Over the years I have taken out my TT batteries and hooked them to a trickle charger in my garage during each winter. I now have the TT under covered storage at a local storage yard which has electric...
I have left the TT plugged in all winter, checking the battery water level, I have disconnected the battery and charged it periodically on the TT. However, the easiest way for me is to charge it and leave it in the laundry room in a plastic tub.
It is convenient to check but only sits for 3-4 months so it rarely looses much charge.