Hi Rafiki!
Replacement sealed-bearing cartridges are available for the FSA threadless headset; I bought several and put them away for a future time when they are needed. I have already revived another old one by dropping new cartridges in the old cups (the old cups stay in place). I have found they also fit Cane Creek units, so long as the cup dimensions match.
Sometimes, the complete headset is available for as little as the bearings. I found this when I bought a second one.
As for headsets, my preferred _old_ favorites for quill stems/threaded steerers were headsets with tapered roller-bearings -- sadly pretty much unavailable these days. My favorite was the well-sealed Stronglight Delta, but if you run mudguards, the Stronglight A9 will do nicely (now redesigned to use shielded cartridge bearings). I also have a Tange G-Master and (bonus points for obscurity) a nice Saavedra rollerbearing headset from Argentina on my tandem. They just go and go...over 28,000 and 32,000 miles on a couple. I use kneaded beeswax as a thread-locking compound on my threaded steerers and have squirreled away 6 pairs of upper and lower tapered roller bearings, retainers, and floating races for the Stronglights. I doubt I'll ever need more than one or two of them, all placed in the lower seat.
If you're really frugal as I've sometimes had to be, there are a number of half-measures to extend the life of a brinelled headset, and I employed most of them during my uni years, when I was consistently riding 8,000-12,000 miles/year for more than a decade. Among the more effective methods: If your headset uses ball bearings, you can switch from caged ball bearings to loose ones (I did right away; the greater contact area of more bearings extended the life of the headset from the start), or you can remove the lower cup (almost always the one that pits) and rotate it 90 degrees and reinstall. The bearings then tend to seat on a cleaner portion of the crown when riding straight ahead. Much the same can be done by re-orientating shielded cartridge bearings on the lower crown seat.
And, of course, riding with mudguards/fenders will extend the life of *any* lower headset bearing by shielding it from water thrown up by the front tire.
All the best,
Dan.
