No doubt, you make some great points.

I agree that finding steel frames with magically unscratchable lenses probably aren't realistic :) I also agree that treating a pair well is the best bet at making them last. The pair that I just broke was my first time splurging on a nice pair of sunglasses and being intentional about treating them well. They lasted me for over two years and I was very happy with them!

The more I see promises like Waterhaul though, I wonder if their Osprey-style guarantee would be nice to have. They have a lifetime guarantee on replacing their frames (probably banking on most people losing theirs rather than breaking them) on top of using recycled materials. Obviously this would not include replacing lenses. Seems like it's at least half way to being a good route?