Hi IanP,
No, I have not replaced any of the chains.
I thought if my plastic lining pieces lasted for 270,000 km then a steel chain will last at least another 270,000 km and I will replace it next time with the next chain guides repair.
To be serious, I have not heard about catastrophic failures of these chains and if it happens to me this Forum would be the first to know about it. I have carefully inspected every single link of the long chain and did not find absolutely any signs of wear or tear – no flats or worn out spots on the rolls, almost no play on the pins, nor even slight wear on either of the staked sides. I always prefer keeping sound original components in my vehicle – this not only brings the cost of the repair down but also keeps original BMW parts made by high standards and workmanship, now proven by time, in place (otherwise at this mileage I would have to keep replacing everything). In my opinion, another advantage of using the original chain is that this chain has been stretched already and will not affect my timing alignment down the road, whereas a new chain will stretch after some time and may affect the timing (it might be just another piece of mind for me to justify not spending extra $150.00 on the chain.)