Mango, I'm relentlessly telling people that typically rotors can go two sets of pads. I'd read many, many threads on this just the same as you, and I'm also quite confident in my measurement of the thickness of my rotors.
They're worn from the first mile, but mine won't be worn out until they're through the second set of pads.
You don't tell people to flush coolant every year. It wouldn't hurt, but it's not necessary.
You make it sound like I'm suggesting something dangerous or stupid or both. Just want the OP to be informed, especially when up against a 'dealer tech' recommendation. His rotors could be worn...they might have had three sets of pads on them already...IDK. I'm not saying he should slap pads on...just that he can measure the rotors.
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Mangofy your E46!