Mine is raw water cooled. I winterize it with automobile green antifreeze 50/50 mix. If it was done right and you used good antifreeze there should be no problem. That said, "no frost problems". Any engine that sits for long periods should be turned over. I ensure mine is once a month...this past winter I put the carb back on (I usually pull it and clean it in the fall) and started the engine once a month. Started no problem -5 C. That ensures the valves don't start to stick etc...keeps it "fresh". Prior years to that I cranked it over on the batteries / starter once a month just to move the valves and pistons... some rpms.
Occasionally I hear of boats who's engines incurred water because water was coming into a hatch and dripped on top of the head...then leaked down through the plugs...this can cause stuck valves and or pistons. Something to consider and a layed up engine could use tarp over the top of it if there is a chance of water draining onto it.
Edit: Your gas? Did you have stabilizer in it. If not it has to be removed prior to trying it...just asking for trouble. A good practice is that every Jerry Can gets hit with 20ml of stabil first
Hope that helps.