Winterizing: blow-out vs antifreeze for longer term storage?

Wrace wrote:
I was kind of hoping I could just disconnect the batteries and leave them there unattended for the duration?

Or I suppose I could check and charge them once each year?

3 years of no use, they will be junk. cycling once per year won't help much. simply be prepared to buy new when you get it out of storage.
But still remove them. If they should freeze and break that acid won't be kind to anything it touches.