The chain on our eng. I had replaced at 269000 miles. the replacement chain broke at 70000 miles. there were a lot of things interfering with each other traveling along at 65mph.
There was a couple small plastic pieces and a couple pieces of chain link in the pan. the chain tentioner and rails were replaced, so don`t know really what happened.
Mike at Metric Motors said the sprokets wear with the miles, and a new chain will wear faster because of them.
Maybe I should have left the chain alone and not changed it, this was before I knew about checking chain stretch.
chains don`t need to be chainged with age, just the miles and wear/stretch. belts is miles and age because rubber does deteriorate with age.
Just stay away from the Chineese junk and get good German chain. there are write ups here on the forum about it.
My 2¢
Charlie ☺