A slight bit of wear is not a problem and is probably only a fraction of what you would see on a regular plug and still consider it good. With some newer ignition systems not putting out the voltage they used to it does make sparkplug wear/gap a bit more of a concern though. I am curious as to what you call "good spark" from a spark plug ? What does a degraded spark look like ??

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)