I've been using wellers tips by 5 to 6 years, the only thing I use is the wet sponge that came with the soldering stations.
I have non constant use, 3 to 4 times a week, some times big boards, some times just replacing a component. I never changed the tips yet...
I read somewhere else that the 'news' tips (from good companies) came with some kinds of plating, that wear out if you use something more hard. Because that I keept the wet sponge.
Always wet, and daily cleaned after work. If I had to choose another, I would go with the brass, because it is softer than other metals...