I switched from the damp sponge to one of those copper 'scouring pad' tip cleaners and couldn't be happier with it.
I can usually keep the temp between 625-700F or so most of the time. Lead-free solder needs a higher temp - as well as parts with more mass - as mentioned above by Optikon.
The iron's tips should last longer if you can keep the temp down. When I have the iron idling for a few minutes (or more) in the holder, I'll usually turn the temp control way down until I'm ready to use it again. It only takes about ten seconds or less to get up to temperature again. And yeah, get some tinner right away and use it frequently. I use it (at least) every time I go to return the iron to the holder.