N57 doesn’t suffer like the n47, I have known them snap but not to same extent as the 4 cylinder.
I did an n57 chain a few months back that was on its way to snapping, so whilst I wouldn’t say rush out and get it done ASAP I would probably plan to get it done by 100k.

They can suffer bottom end issues but as you do regular oil changes not so sure I would open it up and do shells and oil pump.

 

Hi, I am not so familiar with this engine . I have a e39 528i. I appreciate your c9ncern regarding the timing chain . But I am always concerned in breaking the "seal" or the engine as if nothing is leaking , grate. I'm not sure if from a oil change you could find any pieces or even send a sample away to be tested ? That being said its its not the the head of the block and be breaking g such a gasket so may be worth a while . I'm pretty sure you can hear if there are any issues . I just don't like looking for problems that aren't there. Not sure if checking a oil engine change but buy all means it's not a " place " that may leak I believe if done correctly. I apologise that I am basing this thought process on a bmw e39 528i. N52 engine I believe.
I hope it works out for you, best of luck . Would be interested in your progress as despite what I have said I probably need to check my timing chain soon. Unbelievable that they use plastic pls a tensioner. If it runs well and sounds good leave it . Once again I could say more if it was similar to my engine. Good luck

 

fix when it need fixed,never seen any snap ,indy i use aint had many either as i asked him,and he has loads of n57 in,bottom end a different story,3 x5's in ,in 1 week when i was there.again he thinks poor servicing schedule to blame.