I have a temperature-controlled soldering iron. When I use it above 250°C, the tip quickly dulls and won't take solder. By "quickly" I mean "within 20 seconds". I have to clean the tip with copper wool or a damp sponge literally between every joint.
I am using leaded solder, and I only solder at these higher temperatures when the wires/contacts are large and difficult to heat. Or when using desoldering wick, which amounts to the same thing.
Is my tip just of poor quality? I have tried different tips, but maybe they just all suck. Should I be using a more expensive tip?
EDIT: I'm using a MarkEthan SMD Rework Station, with generic Ebay tips, and "AlphaMetals 8-Sn60Pb40" leaded solder.