To file or not to file?

[torikoos]

I concur with Woodone here, keep using a wet sponge, and religiously wipe the tip clean of the iron regularly while soldering, at least once every 5-6 solders if not more often. Especially if you use solder with a slightly acidic flux, this can 'eat' the tip over time, in any case, try to avoid filing plated tips, it will work for a bit, but ultimately will deteriorate the tip even faster.

Loren:
Try keeping the tip clean. I use a sponge that has been wet with water. Wipe it off before each use. There is also a tip cleaner that you might want to try, not real sure of the correct name might be called tip saver or tip cleaner. Try some place that has soldering equipment and I think you will find it.
BTW I solder every day doing DCC installs. I just replaced my firt tip the other day. It lasted almost a full year before I had to replace it. You can also use a paper towel ( wet with water and a little soap detergent) to wipe the tip after (and) before each use. ALSO if you have a adjustable temp soldering station try to keep the heat down. This will save the tip too.