Product review (3 stars): Prone to Sun damage
Most people who install these things probably aren't aware that they're a wear item, like paint.  I made the mistake of touching one of ours outside in the course of routine maintenance, and it crumbled.  It was somewhere between 10 and 15 years old, on a south-facing wall.

If these things were made from ceramic instead of plastic, they would last the lifetime of the house.  They'd also be considerably more expensive.  But I have half a dozen of these vents on my house, and I have more important things to do with my life than replace them.

Note that my review is on the product alone.  This vendor shipped lightning-fast.  Five stars for that service.