Read this -
Cheap vs Expensive sunglasses. As with most things in life, you get what you pay for. Expensive sunglasses last longer, and provide more clarity. They are also better for your eyes (reducing the need to squint for additional clarity or extra glare). The frames are also much much better. I think it is best to own at least 1 cheap one and 1 good one (depending on activity). Frankly this seems to be a warm deal, but there are uses for expensive sunglasses.
Yep. I have had the same pair of Aviators for 25 years and they are still as good as new...