I'm bad...I just cleaned my Lee .223 decapping/sizing die yesterday for the first time ever. I've probably put about 1,000 rounds through it, and I even got a case stuck inside about 6 months ago (due to lack of lube - and that cost me about $10 to have removed). Anyhow, yesterday I took it apart and cleaned it out well with some FP-10. I also cleaned/lubed the ram of my press with it, and the result is far less friction (gee, whodathunkit?). I feel like such an idiot - I change my car's oil every 3,000-3,500 miles to prevent dirt and metal shavings from damaging my engine, and the exact same principle applies here. I guess that I pay more attention to the car because new engines are just a bit more expensive than dies.
I've resolved to clean/lube every single die I use - especially the sizing dies - when I next use them. As for recleaning, I suspect that I'll either do it every 6 months, or every 500 or so rounds.
By the way, does anyone lube up their titanium pistol resizing dies, or is this unnecessary?