Granted. Chain stretch is the gold standard.
The only way to objectively gauge the chain wear.
Finally, I must question your remark about very little need to clean your chain:
As for chain cleaning, there's very little need for that in my case. Teflon does not attract dirt and grime nearly as much as other lubricants.
The key words there were "in my case" and I stand by that assessment. I can certainly understand the need for more/less frequent cleaning when using motor oil and/or most dedicated chain lubricants - that stuff attracts dust, sand and road debris like my grandmother's jam attracts bees. Speaking of my case, here is what it is:
Chain: D.I.D. ZVM2 (about CA$100 more expensive than the worst non-o-ring junk)
Lubrication: Exclusively Dupont Teflon Multi Purpose spray. Cheap, versatile, not messy and widely available. A 5-10 second spray, approximately once per tank of gas.
Mileage so far: 42,000Km, about one quarter on dirt/gravel roads or in pouring rain. I love to make bandit's torque work.
Stretch: Still within spec (~1mm under the limit).
Maintenance: Practically none. Washed once, after 30,000Km or so, just because I was bored.
Adjustment: After first 1,000Km and then only at rear tire changes (7-13,000Km).
Rust: None/never, even after long rides in pouring rain.
Reply: The factory Suzuki Manual 99500-39134-03E says on page 2-12 "Wash the chain with kerosene. If the chain tends to rust quickly, the intervals must be shortened". The manual also says (between two CAUTIONS) "After washing and drying the chain, oil it with a heavy weight motor oil" because anything but motor oil "has too great a dissolving power for this (OEM 'O-ring') chain and can damage the seals confining the grease in the bush to pin clearance".
That's all fine and will do the job, for those that don't know better. Dupont Teflon is safe for o-rings, it says so explicitly on the can. It does not attract dust and grime and it certainly does not allow the chain to rust. About the only recommendation from the manual that still makes sense is the use of kerosene.
Speaking of kerosene, I washed my aforementioned chain with dish washing soap after I took it off the bike a week ago. It wasn't nearly as hard to wash as my previous chain that was lubed with 80 weight oil, but would still repel water even after it was cleaned of all residue. I just hung it to dry without oiling it again and it looks and feels just as good as the piece of the same chain that was never used. BTW, I'm not going to put that chain back on the bike because I already bought a new one, but will keep it as a spare and won't hesitate to use it again if the need arises. It's good for at least another 10,000Km.
Dupont Teflon rules. Until something considerably better comes along (I can hardly imagine any property that could be improved) no chain of mine will ever see any other lubricant, period.
http://www.webbikeworld.com/t2/motorcycle-chain-lube/dupont-teflon-chain-lube.htm The Suzuki manual says the same thing as the Haynes manual about chain stretch, BUT - my el-cheapo plastic General 6" dial caliper
No need for ultra-precise measurement there. A good tape measure and a sharp eye will do the job. I wouldn't take the factory/Haynes manual prescribed limit as a gospel either. For me it's more of an indicator when is the time to order new chain/sprockets and shorten the chain/sprocket inspection intervals.
Maybe I am doing something right.
You sure are. The chain is still in good shape and performs well for your bike and riding style.