[Carl n Susan]

Two things.
1. I never latch the clips on the vent. It is just fine after 11 years of driving and sitting around. Once in a while I will hear it flap if the wind is heavy and from just the right direction.

2. When the vent starts to turn yellow (mine is painted so not a problem for me) simply mask it off and paint it with a rattle-can spray paint. I believe "Appliance White" is a perfect match.