You need to spend so much on them that you're totally obsessed with protecting them! And, get a lanyard.
I had a pair of Smith prescription, bifocal, photochromic sunglasses that I loved. A dog chewed them up a bit and Smith replaced the frames for me. Probably had them for 15 years, and always on a lanyard. The prescription was stale but I still used them.
My nephew talked me into riding a roller coaster at World's of Fun in KC a few years back. I tucked those glasses into my shirt, still on a lanyard, but somehow they flew off. And the punks that work there wouldn't go down under there to look for them. Something about that being dangerous. But, I showed them: I am boycotting The Mamba forever!