Well I don't think I was imagining 40 degree setting in the 172N that I took my instrument checkride in.

Here's something I surfed up:

"...not until the 1981 model year was the maximum flap extension reduced from 40 to 30 degrees."

http://search.netscape.com/ns/boomfr...2FA02P0136.asp

C172Ps were the last of the 1980's Skyhawks, and were introduced in 1981 according to wikipedia. So, my guess is that was where the 40 setting actually ended, when the P was introduced. I never found much use for the 40 degree setting as it slowed down touch n goes due to retraction time. I think they were for super-short field landings which no one does anymore, perhaps a sales gimmick. As far as I know they only only added drag which is of little value when forward slipping because that does it so much better.