Timing Belts and Timing Chains are an essential part of your engine, when they fail on a modern German engine you should bear in mind that the small cost to replace a chain or belt is minor in comparsion to the price of rebuilding your engine.
It has been well documented that there is an ongoing issue with BMW N47 Engine timing chain failures.
A simple google search will provide reems of information and the BBC watchdog investigation into the problem. The simplex chain used by BMW in their engines is just not proving to have the longevity expected of timing chains. The extended service periods reduce the oil quality as well which affects the chain lubrication.
In our experience, We replace more BMW chains than any other brand of engine. Not just the common N47 and N57 Diesel engines but more or less the entire range for one reason or another.