Is this the thread? http://www.thefirearmsforum.com/show...=cleaning+dies
This thread talks about dies for full sizing .223 cases. The lube builds up in the full size die. For neck sizing you don't need lube, so don't need to clean the die, or don't need to clean it very often.
I don't believe I've cleaned my pistol caliber dies and have reloaded well over 1000 rounds over the last couple of years. (I'm not as high a volume shooter as some on this forum.)
Someone else with more reloading experience and higher volumes may have better advice.