Originally Posted by marine6680

Heat kills tips...

But to be more detailed tips are made of a base of copper and a protective plating of another metal Iron or less often nickel or chromium (or in the case of hakko, a double plating of chromium over iron. others may have this as well)

More active metals tend to invade and replace/erode less active metals, in a similar way water can erode dirt and rock. (in result only, the processes are completely different) Copper has a low reactivity level compared to most other metals. (like the lead and tin in solder) This is why tips have protective coating of a different metal.

The erosion process increases with heat, (I think its on the level of doubling for every 10*C) and in the presence of reactive compounds like acids. (flux is a form of acid, RMA is weak compared to other types and is best for long tip life) Iron as we all know reacts easily with oxygen (rust) even at room temp, and acids make this worse.

Cheap irons have iron plated tips, which will wear out quickly, and the more heat the quicker it happens. More watts is more heat, and cheap irons are on or off, temp selection might at best be high and low.

You can also crack or wear away the protective plating by using bad technique when soldering or cleaning the tip. Even tiny cracks will exposes the copper to damage. If you ever need to file the tip, you are in a loosing battle. When the copper is exposed, just a few minutes is enough to put huge pits in it.