On a Japanese seiyuu image board, someone has recently posted a set of pics of 104 seiyuus, in order of age -- from Inoue Kikuko at 46 (not 17, sorry) to Yuuki Aoi at 18.
Here is the set of three photos, showing seiyuus aged from 46 down to 31, from 30 down to 26, and from 25 down to 18. I have spent altogether too much time substituting romanized names for the kanji and kana names. (click images to enlarge)
Birthdates are given, and show that some seiyuus are a year younger than stated, but the order seems correct. And I have added rising star Hikasa Youko, as suggested by posters on the board.
One peculiarity of this seiyuu image board is that for pics of individual seiyuus, it almost never includes the names of the seiyuus. Perhaps that is just otaku pride, and perhaps it is a way of getting around Japanese copyright practices.