I have a Surfas (sp) I bought in 2008 for $160 at a shop. So a relatively early modern light. I've done nothing but use it and charge it and I cannot tell any difference from new. It now takes a backseat to a NightRider that cost about half as much and is far brighter. Times have changed. But it is the most reliable light I"be ever owned. And Surfas isn't even a light company, just a name.
Oh, I did replace the mount. Rotating between 5 bikes and always coming off to charge took its toll.
Ben