I left my stock chain on for 6500 miles, I can't say it lasted that long, but I left it there that long. I lubed it every 200 miles and cleaned it every 1500 or so. It was total junk when I removed it after a great multitude of times readjusting it.
I went to the 18T and a Tsubaki O-ring chain. It may be the cause for an occasional miss of a downshift. The extra drag would do that and it may even cause a slight reduction in performance and mileage. On the other hand, I haven't had to adjust it in 5000 miles, and if it's typical of the other O-ring chains I've owned, I can expect well over 25,000 miles out of it.
I guess I can blip the throttle on down shifts.
When it wears out, I'll consider a non-Oring chain.
I probably haven't boiled and waxed a chain since about 1963. Useta, though.
Bare