70-200 VR I High-pitched noise - fatal?

Hi guys, a little help here...

I recently sold my 70-200mm 2.8 VR 1 and the buyer now says he notices a high-pitched whistling (whining) sound coming from the AF motor when focusing, especially from afar to close. I suspect he's trying to describe the following (YouTube video):

http://www.youtube.com/watch?v=DfV2snLogkE

I must say I haven't heard this sound or ever paid attention to it. Is it a bad sign? Should I refund his money? Give him discount? The lens is from 2008 (even a bit earlier), could the lens be at the end of its lifespan or is this nothing to be worried about?

With anticipation,
Kimmo

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