I have Oakleys Flak Jacket XLJ - I know they are ridiculously expensive, but all parts are replaceable, and the number of lenses they have is overwhelming. I use polarized grey lenses for day riding (in combination with helmet's dark smoke shield ), and persimmon lenses for night riding, or any other activity that requires eye protection without decreasing the light (shooting, working with power tools)
There is definitely some additional stress on the frame of the sunglasses when worn under helmet, but it's been 3 years and no problems so far.
I have a history with sunglasses - the really cheap ones would bother me and I would even get headaches. So I went to more expensive ones - well, I also tend to do things like leaving glasses on driver's seat and then sit on them - that's how Ray Bans went. Then I got ridiculously expensive Revos. Had them for a week, went jetskiing let off the throttle too quickly, the glasses just went flying off my face and into water. Another time, while whitewater rafting, poured a helmet-full of water on my head, and off the glasses went.
Now that I have Oakleys, I've already sat on them, dropped them many times - they are still going, and if they break, I can just replace the part that is broken. Oh, and they have some weird compound on the arms that sticks to your skin a little.