I have the RecTec cover for the bull and leave it outside all year long, the only thing i have noticed is that condensation does build up under the cover. But it has not caused an issue with the grill or the pellets yet. I just take the cover off on nice days to get air in there.
I have been using the Gunter Wilhelm 12 inch slicer I like it a lot, just have to make sure when you sharpen it you use the correct angle it is 15 degree knife.