I finally had to take steps.
When one CD takes up nine slots on the Top 25 Most Played playlist, and the other songs on the CD are tied for the bottom slot, and ready to force other songs off the list the next time the CD is played, well, it's time to do something. That was what was happening on my iPod.
With all tracks having play counts between 37 and 41, Susanna Hoffs' 1991 solo album When You're A Boy has now been declared the grand champion, and the play counts for the album have all been reset to zero. Yeah, I love that album to death, but if I want to listen to it, I can just select it in its entirety (which I frequently do). It defeats the purpose of having a Top 25 playlist when one album shoulders its way onto the list.