Knowing what I know now about dentistry, I would only ever let a dentist drill a tooth where I can actually see decay. If I can't see it, and the X-ray looks dubious, I'd just outright refuse. And then I'd see another dentist.
Exactly. One time I skipped out in 2-3 years of cleaning while dithering on finding a dentist in the new area I moved to. She presented me with an estimate involving about 8 fillings. (I had specifically asked her to keep to the necessary ones.) Shocked, I went back to my old dentist for a second opinion. He told me most of them must be just replacing amalgams with porcelain because he couldn't find any actual new decay.