Hi - I am building up a Lemond Tete de Course and I plan to do so with high end parts on the cheap (i.e., Ebay , Craigslist, etc.). The question I have revolves around used headsets. I'm looking at picking up a Chris King NoThreadless Headset 1 1/8".

I see some used ones on Ebay - are there any concerns with buying a used headset?
Anything to look out for?
How long should they last?

Thanks!