I keep my boat in a detached garage. As long as it is in the garage I keep all the compartment lids open. This way all stays dry and or dries out after I have fished in the rain. The only line problem I have noticed is deteriation through the heat of Summer. While fishing a small club tourney in September, I felt like I was fishing with rubber line. I had so much heat built up in the garage during those 90+ degree scorchers that it had to be the problem. Re-line all reels and solved the problem. This Spring will probably add a roof vent into the garage. So "My Opinion"-- Not so much the cold, but the heat as a deterioration factor. Have also heard that a good soaking of your preferred line lube, (WD-40, CDP ETC.)can add some protection in extreme cold or heat.