Q: alternator

The bearings in the alternator will probably become noisy prior to the electrical components going bad. So, if you value quietude, there may be an advantage to installing a new alternator prior to "complete" failure of the part. Apart from that though, there is no advantage to early replacement of a working vehicle alternator excepting the perhaps obvious advice that if the alternator is markedly noisy, replace it as if the bearings seize the serpentine belt will probably break and then you could be stranded. The best replacement alternators are OEM new or remanufactured ones supplied by the car dealer parts department. In regard to your question about service life, a well manufactured OEM alternator from Toyota, Volkswagen and so forth will easily last 10 to 20 years but, again, beyond that point it is not so much that they will necessarily break and fail but rather the bearings get noisy. If you desire an evaluation of your existing alternator and advice as to its condition, please request an alternator inspection/replacement. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.