My bonnet seems fine. No scratches, fading, nothing. Surely it would depend where you park you car? My drive outside my house is covered most of the time by nearby houses and when out and about I always try to park in the shade, not because of the bra, more the fact that I take care of the car and wish to prolong it's life.
As for water, never really had a
problem. If it was causing a
problem I would be taking it off.
The only time it comes off is when I wash the car, re polish and seal the paint. Give the bra an inspection inside and out before fitting it back on.