When "the regulator goes bad," I believe it is usually just that the brushes (part of the regulator) wear out. That is easy to see visually once you have it out.

Yours is a water-cooled alt, right? I remember seeing a thread on here not too long ago, where there was a bearing failure on one of those, at a fairly low mileage. You might want to consider that as something to preemptively repair.

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2001 X5 3.0i, 203k miles, AT, owned since 2014