Factory axle lasts some 300K miles if dirt is not allowed to enter.
Some people routinely replace CV boots every 100K as maintenance.
These axles last forever.

Axles from local parts store are usually made in China, it is hit or miss...

Don't wait. It will be an expensive lesson.

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1998 E39 528i 5sp MT
2006 E53 X5 3.0 6sp MT