Don't all sealed bearing headsets not sit tight and need to be compressed slightly for the bearing to sit in the cup. As far as I can remember the bearings have always (or at least for a long time) had a conical area on which they would make contact to an equal area on the cup. Top half on the outside ring of the bearing, bottom cup on the inside ring..?
I've never used loctite to get the bearing sit tight in the cup. That's what the little amount of preload is for (starnut or similar thing in the steerer tube).
I still have the feeling I'm way off here...
But true, some 2100 miles, likely quite a bit more if you don't record all your riding, isn't too bad in my books either. Usually headsets last me about that distance too I'd guess, but fail quite differently... shear into fragments at the contact area or just split apart.
This was a sealed bearing (regular SKF) after about 4000 km or so...
If you still have the bearings you might find a number edged on the bearing's wall. This could help you find a replacement from standards as SKF.
I'm running a Slackeriser from Superstar on my Kona which has been running smooth sofar, but only had it installed this summer. A bit early to say how it lasts. Shame Superstar (from which I once thought I'm not going to buy anything anymore due to regular problems with their hubs), don't make a 1, 1.5 ° angleset.
