750i OEM spark plug change interval.?

Hi!! Everyone, so i dont get any info on my car spark plugs, bought car eight years ago and went to injection system shop, and they sad that this OEM spark plugs can go about 100k km, so i changed it after 67k km, and now drove 45k km and buy new one again, but i take out the old spark plugs from car and they look like new, so i make a call to my local BMW dealer and ask them, about spark plugs change interval, but they cannot answer to my, how i can go on spark plugs, so maybe you guys have some real info on that.



Thanks.

750i OEM spark plug change interval.?