It seem's most of the pic's I see of the interior of ute's and van's, the vent's in the dash have faded to white around the edge's. HJ onward's I'm referring to.Even though the dash is in good order on most of these,the vent's look worse for wear.

Would this be caused by sun exposure,or just the ageing process,given that they are in their thirty's now?

Cheer's.