I think you should change it. I agree that it won't necessarily prevent a transmission failure, but the cost isn't that much if you do it yourself, and it gives you a little peace of mind.

I have an '05 4.4i just like you. My manual says that the transmission fluid should be changed at 100,000 miles, not lifetime. I just changed my filter and gasket, filled it, and drained and refilled it again. With BMW ATF. It wasn't a complete fluid change, but it seems to shift more smoothly. Not that it was having transmission problems before.

It's your call and it probably doesn't make a big difference either way. I'm for fresh fluids, changed regularly. The ATF may last forever, but for my ride I want all fluids to be as close to original spec as possible. If the tranny dies anyway that's just my bad luck. At least it wasn't due to old transmission fluid.

__________________
2005 X5 4.4i black on black
2003 325Ci black convertible