I had the CK threaded headset that is not a conventional setup installed on my custom. It never went further than 200 miles without needing adjustment in the 7000 miles I rode it. I adjusted it. Several pro mechanics adjusted. I took it to the Chris King factory and let them adjust it. Finally pulled it out and put in a Tange. Sadly, the stack heights didn't match and I had to mix and match several different Model Tanges. (Thank you, Tange, for making that so easy!) I did a tweak after riding around the block and might have touched it once in the past 6,000 miles.

Tandem Tom, are you sure you haven't tightened the Levine down too much? One year sounds like way too soon unless you are putting in monster miles. (I did used to go through about one headset a year on my racing bike doing ~5000 miles/year on New England roads with a 75 degree head tube. Didn't matter if it was Levine or Campy NR.)

Ben

As far as too tight? I can't say I remember but it will be correctly adjusted this time!

As a precaution against the headset adjustment becoming too tight, I recommend tightening a quill stem, by itself, into the steerer. With the quill in place, and the adjustment then secured, there will be no chance of the adjustment tightening up when the bars and stem are finally installed.
The stem by itself won't mask a slightly-tight adjustment the way that a complete cockpit setup can (cables are huge offenders). Removing the front wheel to give the assembly a final check before the real stem and bars are fitted will give a good read on just how much bearing pre-load actually exists.