Shane - I also use the Weller 40W Irons, and i have been on the same iron for about 2, maybe 3 years now. At all the races, i plug it in when i get there, and unplug it once i remove the pack i used in the main.
I don't even use a sponge.. call it "Paper Towels" wetted with my Pepsi
I just make sure to always have the tip clean and tinned, and it never fails me. The tip is accually on it's last leg though. When it started that stuff on fire at the Novak race, someone took a file to it while i was gone, to remove the burning plastic. That removed the plating, and it oxidieses pretty quickly now
I'm accually looking into a new Iron though, more so since i need something nice, and need one that comes with a stand. My sheet of aluminum and my weller iron could be dangerous