Thanks Duncan.
As an addendum, I would like to add that under normal PCB soldering (not heavy wires) I actually run my iron at 250 to 275.
I put it up to 300 for heavy work with thicker tips.
I have an 852D which is inexpensive. Many companies put their name on it but the model number usually remains constant.
I haven't had to change the hot air or the wand elements yet either, even though it came with spares.
The tips of course should be replaced as soon as you notice that the plating has worn off, although they will continue to work after.
I was searching for something else completely on the web when I came across this post, and thought I'd put in my 2 cents worth.
I do a lot of soldering, and my latest little project had probably about 1500 solder joints in it.
Having a tip that won't tin would be a huge problem.
You're probably wondering what would have so many solder joints, so here's a quick clip of it.
http://www.youtube.com/watch?v=bxUShTWB9UQ
If anyone has any other questions for me, please feel free to ask.
Always remember that a tinned tip transfers heat much faster than a hotter untinned tip.
It's the same principle as putting heat sink grease on a heat sink. The solder acts as a thermal transfer conduit.