I for one take mine down every year on the 2nd January. I know some may say I should wait until the 6th, "it's bad luck" one year I left mine up until March and I can't remember getting more good luck!
Get 'em down as soon as possible that's what I say!

I take them after Jan 6th, that's when the Three Wise Men come with presents! ^_^

First or second week of January. I don't like leaving them up too long, as it keeps me thinking that it's the festive season and I don't have to work.

Wait. I don't have a job. They're staying up.

Okay - FullAuto has a point here, I'll leave mine up and stay off work. I like it!