Originally Posted by X5SilverBeast

Yeah I know it does sound overkill, but for piece of mind, I say the hell with it. I've heard some M5 guys do the same. Thought I do the same and see how it runs compared to 50K or more. I've done this with the 540 since I bought 3.5yrs ago. I've put over 100K miles on it and she still purrrrrs like she was brand new. I think I have OCD when it comes to car maint.

The last time I went to the dealer just to see what they charged, $25ea sounds outrageous for the 540. I've used bosch plugs before and they had the tendency of backing out. Had really good luck with the NGK's. I've already done plugs on the X after the wife and I bought it. Had 78k in march and now at 94K. Probably change around 100-110K, but may go a little longer since the X's plugs cost more.