That's my theory! It depends how well you can pick up on faults and the way the car drives tbh, the reason people recommend 70k is that that appears average some go well before. I guess if you cannot tell by feel or can't do the tests you should either pay someone to do it, or do as advised treat it as a service item, cos if you can't or don't, pick up on it failing it will get expensive! I know from experience on different makes and models what seizing VCUs, LSDs etc feel like, and having a freelander that's just started doing it its pretty obvious to me! But may not be to you! So you need to decide the best course of action for you, just bear in mind it'll be an expensive mistake if you miss the signs!