I have a slide topper on my Lance 1121. It has kept the slide dryer during the rainy season in Fl. while offering some shade from the sun; kept out the leaves, sticks, pine cones and needles in the WV & Carolina mountains during the fall; kept the snow and ice out of the slide in NY and PA during the dead of winter. Unlike other RVs, a TC topper is relatively small and I've never been annoyed or concerned with high wind. Several years ago, I camped in Ohio when the remnants of hurricane Ike rolled through with 60+ mph wind. The topper kept a lot of debris out of the slide and I never heard it floppin'.
Only once have I needed to address an issue. While camped during the winter in NY, my slide was out for a number of days. I'm a Florida boy... what do I know about snow? Had plenty of it though with temps hovering around freezing. The snow partially melted during the day and froze at night. The eventual build-up of ice on the topper was a problem when bringing the slide in. Today, I simply run the slide in and back out once a day under similar circumstances. Count me as a believer in slide toppers, particularly for a TC.