On average. Once a month or more. Every couple months or so. A few times a year. Every year. Every other year. Every few years. Once every half a decade or so. Less often than that. Huh? Replace glasses? I'm still wearing my first pair. I don't wear glasses. View Results Mine normally start falling apart after 3 or 4 years, so that's generally when I get a new pair. --- Stupid signature!