The chains we used on the TA were 9 speed chains and all three of us made the trip on one chain and used the same chain for a lot of miles after. I know that two of us got 10K miles out of those chains and the other rider in our group used the same chain for quite a while after, but I do not know her mileage. I have not kept good track of the 10 speed chain on my road bike, but it seems to be holding up quite well too.

I actually had worse life out of the 7 speed chains that I have used. It may be that they weren't as good of a chain or that I didn't care for them as well.