The thread on "Hot enough to melt lead" reminded me of this one from one of my middle school or high school English classes. We were called upon to think of alternatives to "As old as the hills" as something that seems ancient to us. One suggestion from the teacher was something like "As old as the (whatever doodads) on Grandmother's shoes." That went over like a lead balloon with me because my grandparents wore shoes just like the ones my parents and I wore, and it was pretty much the same for my classmates. We had no mental pictures of whatever was on the hypothetical grandmother's shoes. "Old as the hills" was about as good as it gets as far as we were concerned, because the hills themselves are very old and we all know it, and we are familiar with them. I don't know whether the teacher came up with that on her own or whether she was pushed into it by bureaucrats who come up with new wrinkles to justify their jobs.