I don't know what kind of temp your weather gets down to in your neck of the woods. I live in California and eventhough its not a huge problem out here I still drain the water from my block and exhaust manifolds before I put my boat away for the season. Blocks and manifolds that are left filled with water in freezing temps during the winter months have been known to either push the freeze plugs out or even worse yet crack when the water freezes then expands and has nowhere to go. I open the petcocks on either side of my block (they're located next to the motor mounts) and then I pull the water hoses on the bottom of my exhaust manifolds. IMO, its better to be safe than sorry!

really? Pull the drive for winter storage. Check gimbal bearing, grease driveshaft yokes.

The drives should always be left down when not in use

Even though Winter's about halfway through, I just remembered today about the battery. Should I have that on a trickle charger, or checking it's charge to keep it fresh for Spring?
Thanks again.

Ideally, a battery tender or other automatic trickle charger is the way to go for storage and between uses, it will keep the battery at 100% without overcharging.