I personally think the boots can be effected by many repeated tight turns that one might encounter on a regular basis in a tight space, that would not otherwise occur when just driving around. That you original boots went bad at 45K, getting 30K might not really not that bad. Also $590 for the job does not sound too crazy though obviously one does not want to incur the cost often. I recently had torn front boots and just replaced the axles with Cardone Select. The job is not at all fun, but doable. I picked up a Harbor Freight Rotary hammer, and used it in hammer only mode, and it pushed out the axles from the hub, using a bull point chisel rather easily (rather than manually hammer on it.) One of the reasons I replaced the axles, rather than the boots, is replacing the boots is a real mess...also, if the boots were torn for a while, the worry of contamination and pre-mature wear is obviously a consideration.

If you have worry that the CV joints are worn and making noise, the replacement axles might be the best option if you are unsure. I first was going to save my original factory axles, and put new boots on them once they were out, at my leisure, and keep them as spares, but ultimately decided to toss them.

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2003 X5 Sport w/Premium Package M54 3.0L 6cyl