For those that camp in snowy areas, the toppers then can get stretched due to snow. However there are inflatable wedges to put under them to keep the weight off. We camp year round and have only had about 2" of snow on them, and they are fine. Heavier amounts would be a problem. It's always amazing to me to start the slides in and watch all of the junk on top of them fall right off the front. Lots of stuff you don't see from the ground. They also help keep the tops of the slides drier as well. One thing I have noticed is that some of the factory installed toppers are a thinner material than some of the ones my dealer has put on. May just be the particular brand though. But I won't ever own one without them.
2012 Sandpiper 365SAQ weighing @ 15k, Onan, 2nd air, slide toppers, TST
2013 F350 6.7L Lariat 4x4 CC DRW,Viair 1007, Ride-Rites, Edge CTS, B&W
2001 Chevy 3500CC DRW 4x4, 8.1L, 4.10 gears w/ Detroit TrueTrac
2001 Ford Excursion Limited 4x4 7.3L,V/B Spring Mod, ProComps, Hellwig Swaybar, & other 'Necessities'