Biggest reason for ruining a tip is applying to much pressure. The tip isn't vice grips to hold something down with a lot of pressure. Light pressure is all that is needed, just maintain contact so that it transfers the heat to the solder and connections.

I've had my iron for 4 years now, and pre-lipo days it would spend the entire day turned on. I have 3 tips and the 2mm tip is the one that is usually on the iron. It still works as good as the day I bought it.