If the PPMs are showing people instantly tuning from unfamiliar music, that's gonna be hard to argue with. I've seen some of that but I've also seen it go the other direction... the statistics will be interesting to follow. That's certainly the logic behind licensing a song for use in a commercial; as people get familiar with the song, they want to hear it on the radio.
Your P2s and P3s are going to love a tight playlist at first, but your P1s may get burned really, really quick... from my two experiences, I'd say 3 - 4 days... way too fast for casual cume-ers to even notice you've repeated a song.

I would think it would be hard to balance that; perhaps with a promotion campaign three months in after you expand the library saying "now more variety / listen to us now!"? I dunno.
As many thousands upon thousands of songs have hit the charts, gone to #1, etc., it just seems like it ought to be possible to create a "nothing but mega-hits" format that knocks it out of the park with every song. (I know, I know, just broke the "seems like" rule!)
I suspect sometimes we program a song because it "sounds" right when it didn't chart that high, or skip another song that may have gone to #1 for "X" number of weeks because it doesn't sound right... forgetting that people listen to the radio for songs, not a sound.
I've been shocked to research songs out of previous decades that AC & oldies stations have just beaten to DEATH, only to find out they didn't break the top 10. Other songs that made the year-end charts, maybe top 10 for the whole year, have disappeared from the radio.
What if we really just played #1s? It's hard for me to understand how you miss your target if you're only playing songs that sold a million copies, or two million copies, or whatever. ...and it seems like there would be a LOT of songs like that in just about any genre, although I'll confess to not having counted. ;D
After my posting I went and looked at The Research Dr.'s archive and found a post labeled "Familiar Music" on this page:
http://www.rogerwimmer.com/researchdr/f1questions.htm
It says in part:
...What I usually find is that most people say they like to hear new music, but in reality,...
...when radio stations play a lot of unfamiliar music, the listeners complain that they don’t listen to the radio station a lot because the music is unfamiliar...
...Overall, the research (and Arbitron numbers) tends to lean with the side of not playing a lot of unfamiliar music. But there are always exceptions....
On a personal note, I LOVE being able to discuss this stuff with you! I still remember driving through Joplin in the middle of the night and calling you up to compliment you on how great you sounded... and talking about me wanting to start my own radio station (loll... so much for THAT). :
How far we've both come!!!
I respect and admire your work, and your thoughts; thanks for being willing to debate radio theory with me! After all these years, I don't think anybody's fully figured out how to tame the constantly evolving animal known as the radio audience...