Thanks all, for your opinions!

Bcred, I understand you, that is how I normally maintain any of my cars. That being said, I have found (for me) that my BMW is a bit different from Japanese cars, and even other German marques like Mercedes.

In most previous Mercedes, I would do what you do, and had no problems maintaining things on a part-by-part basis.

That's why I originally scoffed at the notion of replacing the whole cooling system at x number miles (pardon the pun). Then after the first few pieces started going, I saw why.

So now realizing that the X5 is the worst built car in the world (just kidding), I am trying to get a feel of the unique maintenance quirks these have. I havent become a paranoid nanny parts changer because of my experience, I still do a cost-benefit analysis in deciding whether to replace a part pre-emptively. To this end, everyone's collective experience is invaluable!

You might also want to factor in how you travel. If you are about to take off 6 weeks on a coast to coast trip and you have 100K or 10 years on your X, then you would probably be wise to be preemptive and replace all hoses as well as several other things. Don't want to get stuck in the middle of Utah or Montana needing a replacement hose from BMW. On the other hand, if your typical commute is 3 miles down the road to your office and you are confident in your abilities in coping with road emergencies, you can probably afford to roll your dice if you wish and just replace hoses as they blow.

I just completed service at 245,000 miles and will do a more complete posting about the work, but this service included replacement of the heater hoses for the first time. (It was easier to replace the steering shaft U-Joint with them off too) I also replaced the expansion tank (2nd time) and bypass hose on this service.

The upper and lower radiator hoses were done at 150,000 miles and the 1st expansion tank and bypass hose were done at about 100,000 miles.

In each case, all the hoses were inspected at the time, and replaced based on feel and appearance. None were ever found to be at the point of failure - the expansion tank has always been the first thing to leak.

2002 X5 3.0 245,300 miles
2004 325i 109,000 miles