MOTM

A question for those of you who have done lots of soldering with Weller
irons: What sort of life expectancy do the tips have? I'm partway through my
eighth MOTM kit and the small conical tip for my Weller seems to be wearing
out. (I've use it somewhat longer than for these eight kits, but not much.)
The first couple of millimeters refuse to wet with solder any longer, and it
doesn't seem to heat up a junction effectively any longer. It looks a little
brownish, and I can't seem to clean it with the usual damp sponge.

Is there any way to revive these tips? I know that you're not supposed to
file them. But it's Saturday night on a three-day weekend, which means I
can't get to the electronics store for a replacement until Tuesday at the
earliest, and here I am almost finished with a 380 Quad LFO...

Thanks--
--Adam