I had the OEM Chain and the sprockets changed yesterday. Front was second sprocket, rear was original.
My mileage was 76,180 km or 47,336 miles.
The chain and rear sprocket were in excellent condition and my mechanic said there was no reason not to use it for another 20,000 km/12,000 miles or more.
I decided to change it anyway since we were doing both tires and the front sprocket needed to be changed. For the new chain (Oem replacement kit) I will aim for 100,000 km or 62,000 miles.
Okay I didn't make it to 100,000km/ 62.000 miles.
I had my chain and both sprockets replaced this eve. The bike had 163,348 km on it so the chain had 87,168 km or 54,163 miles. Still think that's pretty good and to me it means that for my riding 80,000 km or 50,000 miles will be my normal expected chain life.
If you care to read here is why I had it changed today:
Over the last whiles my chain has been working just fine. It was feeling a bit "rough". (Hard to explain) but I figured it should last until my next tire charge, which will be in the next 3 weeks (before heading down to the Ironhorse May 16th .)
I adjusted it a week or so ago, which is rare so starting to tell me it might be time. On this past Sunday and Monday I went for some short rides (maybe did about 300 miles) and noticed the chain needed adjusting. I adjusted it. On Tuesday it needed adjusting again so to me that meant change it. Today was the first chance I could get it done. I bought the replacement OEM chain kit shortly after replacing the original chain and will buy a new kit sometime soon.