As mentioned upthread, Stronglight A9 is the way to go for a long lasting threaded headset. I have one on the pink magenta bike that's 12 years old. I had one on the red fixer, but that died (the bike, not the headset), after being taken roughly from behind on a roundabout. It's all to do with the use of roller (?) bearings, instead of balls, together with angled faces for them to sit in.