I'm not familiar with BMWs of that era, but other German cars from that era, the plastic cooling system pipes will likely last forever- they don't corrode or crack like metal pipes would over time.
For really critical things like through hulls below the waterline on boats, plastic pipes like glass filled nylon (Marelon) are considered safer and more reliable than metal, because they never corrode, and are much physically stronger than a comparable weight metal part.
I grew up with 1970s European cars where every plastic or rubber part would fail eventually, but by the 90s the materials got much better.
that's good to hear! it's the only weak spot on that engine M44, and that particular plastic cooling pipe is in a nightmarish place right up against the firewall. Need tiny hands if you want to replace it while the engine's inside.
For really critical things like through hulls below the waterline on boats, plastic pipes like glass filled nylon (Marelon) are considered safer and more reliable than metal, because they never corrode, and are much physically stronger than a comparable weight metal part.
I grew up with 1970s European cars where every plastic or rubber part would fail eventually, but by the 90s the materials got much better.