I am using such a weather protection for my multifeed (Poty + Astra LNB).
Works very well especially if it is raining or snowing.
As far as I can see, there are no noticeable negative effects.
Unfortunately the most hoods are made from plastic that will brittle and crack after two or three years because of UV radiation and wide temperature differences over the year.
Last month I tried a desk pad from IKEA (Polyethylene) and cut out the hood.
PE isn't optimal but the desk pads are a cost effective slution as a spare part.
Will see how long it lasts...