I try to follow a personal mandate that if the locals don't wear'm, neither do I. So much communication is based on eye-to-eye contact, I prefer to let my eyes adjust to the light and go without. That said, sometimes ya just need the protection. There are no glasses out there that won't scratch, break, get lost or nicked over time. Cheap is fine as long as optics aren't an issue, though most plastic shades have decent enough lenses to get by until they get roughed up. Smith, Zeal and a few others make lower price but well made kit. Oakley does too I guess, depending on your price range. I try to look for close-outs on name-brand gear from outdoor resellers whenever I'm in the market; keeps cost down and quality up.
The best way to make'm last is use a hardcase when you're not wearing them, and only clean them with the proper cloth - cheap or pricey, they'll always last longer this way.