I use my TomCat all year long down in Oklahoma. The air temp gets really low, but the Wallas usually heats up the cabin so much that I keep a window or two cracked open.
Winter gives me almost my own private lake. As for bugs and spiders, there are few to none and it's easier to keep warm than to stay cool in the mid summer. I also see lots of wildlife in the winter.
I am amazed at the number of huge boats that are left sitting from October to May here in the MidWest.
While some of you NW experienced boaters tip the prop up and out of the water in the winter, the local experts in this area have told me to keep the outboard leg down since there is a continual current of warmer than air water flowing from the depth of the lake, up, and around the boat, preventing freeze-ups here. Just 60 miles North, however, it is not advisable to keep boats in the water year 'round.
So far, two winters down the road, and no problems running year 'round.
As for winterizing the head and water supply, I use RV antifreeze to flush the head and drain and bypass the hot water heater, and run RV antifreeze thru the water pump and all lines. I disconnect the livewell pump and the wash down pump, drain the lines and shut off the thru hull fittings. I use bottled water in small or 2.5 gallon size to cook and wash up.
btw, the small, Cobb charcoal grill goes a long way to warming the cockpit while cooking dinner or fishing, but you have to leave the canvas sides open when using charcoal.
John