I've also found that when you drop in excess of $100 for a pair of
sunglasses, you have a tendency to take better care of them too

Man, that's the truth. I went thru clip-ons like they were socks, and
finally bit the bullet 4 years ago and bought prescriptions. Havn't lost
them, and they're still in one piece. Course, now I need
bifocals...aarrghh