Chain stretched (wore) unevenly. At 4,750 km, most part of my chain has stretched to 0.5%; about 20% of the chain is still under 0.5% elongation, however, while few sections had gone as far as 0.75%. Checking just a section, therefore, is not enough; I ended up checking every pin, and I’m glad I did.
Drop-style chain checker tool is simple, reliable, and cheap—there’s no good reason not to own one if you love your bike. Note that most models available (at least here in Indonesia market) only provide 1% and 0.75% elongation measurement, and therefore only suitable for 10-speed and lower drivetrains. For 11-speed and higher, a checker tool with 0.5% elongation measurement is a must—it’s the point the chain needs replacement, as the drivetrain has tighter tolerance to imperfections.
In term of lubrication, molten wax is king, but too much of a headache for me. Drip wax comes second; not as good, but much easier to work with. Wax keeps the chain and drivetrain so clean, I’m not going back to oil! I used dry lube before—the most common bike-specific lube type available on the market—until I learned that they actually accelerate chain wear! Wet lube, technically, is superior to dry lube, but I’m not letting my beautiful bike stained by black gunk and grime that it resulted.
Few fellow cyclists use a step higher-speed chain on their drivetrain (e.g. 10-speed chain on 9-speed drivetrain) to increase lifespan and reduce noise. I haven’t given the idea a try, however; with the price of 11-speed chain already high, 12-speed chain would be too much of a price for such a marginal gain.
Seeing people waiting to replace the chain until it snapped (over and over!) makes me cringe! If that’s how they treat the thing and the one they say they love… now I cringe even more!