Been there and done that! I forgot to retract the slides, it snowed overnight was time for me to leave the next morning and I had to get the snow off the slide out toppers to get the slides to retract. No ladder so I had to climb up to the roof via rear coach ladder. 6" of snow and ice up on the roof and it wasn't fun brushing the snow off the toppers. If you leave your slides out and if there is any moisture on the slide out topper and it freezes you then risk damaging a slide out seal when you retract your slide. Did that many years ago rain storm, then it cleared up and froze when I retracted my slide ice cut a hole in the slide out seal. Just close the slides you will be better off IMHO!