I don't know the life of chain...??
I changed mine at 25000, couple of months ago, because of the O-Ring failures.
Sprokets and Chains looked O.K. to me, no wearing whatsoever.
Just worried about the o-rings >> don't know why those o-rings were failing?
I guess that I rode on the rainy(little snow) with alot of sands.
And I had not cleaned the chain afterwords for couple of weeks >>> that might caused.

When I tried to clean chain, I found many o-rings were tearing out from chain links...