20 trips = 40 cycles as we re-stalled the cranks to ride around home too.
I am stating what I observed and experienced.
I can't give exact quantifiable data as to how much the chain line changed, but I know that I readjusted the front derailer stops and the JumpStop 10 times during the life of the crank. The cranks had around 52k miles and were replaced a couple years ago along with the bottom brackets.
We are now using Octalink BBs and cranks, so I don't see any movement in the chain line now.