Mine has almost 150K on it (N62) and not a peep from the timing chains.

So saying that most fail between 100 and 140K is nonsense. Most of the chains/guides I've heard of making noise are past the 150k mile mark.

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Current Bimmer
2004 X5 4.4i Sterling Grey Sport/Premium

Past Bimmers
1991 318I Alpine White
1995 740I Alpine White
1991 525I Schwartz
1998 323IS Scwartz
2004 330CI Cabrio Titanium Silver Metallic
1995 540I Schwartz
2000 Z4 3.0 Titanium Silver
2000 330ci Coupe Titanium Silver