I had one of mine clicking for over two years, and I've only just recently replaced both CV axles. Not because of any issue, just because of the clicking (so I knew it was on its way out) and had the time and (most importantly) the inclination to do it.

Having never replaced one before its not as bad a job as I thought it would be. Its actually more of an effort unbolting everything than replacing the axles.

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Present:
01 X5 4.4i
07 Yam R1

Past:
89 R32 Skyline various mods, running 442 BHP
00 Merc CLK55 AMG
01 E39 M5 Haywood and Scott silencers
02 E46 M3 Supersprint Cats, Eibach Lowered, Thorney Motorsport Remap, running 368 BHP