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The #1 killer of soldering irons is oxidized/corroded tips. If the tip of the iron is oxidized it is useless, and you will only damage your project if you try to use it. Really! Don't even think about it! Much like trying to remove a stripped screw, the more you try the worse it will get. The best thing to do is replace the tip or iron, usually getting a new tip is cheaper
Unplug the iron or turn it off when not in use, this is pretty much the biggest deal, if you leave it on overnight you'll destroy the tip.
Pen irons are 'stand alone' tools, they basically have a heating element, a handle and then a plug that goes straight into the wall. They don't have a temperature control (for the most part) and take a few minutes to heat up. These are low cost, but easy to store and use.