I swear by the SL2 model of Smith Sliders. These are made for a smaller facer. They don't budge even on a long fast rattle-you-to-the-bone downhill, give me good eye coverage (important for contact lens wearers), and don't hit my checkbones. I think I have about 4 colors of lenses all of which have been used. I wouldn't buy expensive glasses that didn't have interchangeable lenses.

I always keep them on Chums so that they're either on my face or around my neck. Seems to lessen the scratch and sit factor. I've been getting 5 years per pair. That makes it only about 20 bucks a year.