I would be concern about leaving slides out in winter. A couple of thoughts, and I may be way off base, but:
1. Snow loading and a cantilever effect if you got a major snow fall
2. Exposure of seals to dry, cold weather with UV exposure
I am sure more people with more knowledge and experience will chime in.
2016 Chevy Silverado 2500HD Duramax LTZ Z71 Extended Cab, Long bed
2012 Dodge Ram 1500 5.7L Hemi (with K&N Air Intake) (traded)
2012 Rockwood 2109S (Sold)
2014 Cougar X-Lite 21RBS