Length of play for single-level adventures

[ericthecleric]

Parts 1-8 (and 12) will raise PCs two levels each by the end of each adventure. If they each take, say, 8 sessions to play, would parts 9, 10, and 11 (which raise PCs 1 level) each take 4 sessions to play?
The reason I ask is that I’m sharing DMing duties for this AP, and I’d like to know roughly what the most even split of adventures is in terms of playing time.

[Hierophantasm]

The later adventures might very well take less time to run, but the reason, it seems, is that it is because the later adventures might very well be "stat block heavy." That is, because of the meatier stat blocks for creatures, the adventures might very well be shorter. (Without giving away any spoilers, the BBEG in Age of Worms had a whopping three-page stat block.)

On the other hand, they might not be so much longer, as they are less experience-rewarding. If you look at the experience tables in the DMG, the first few levels see a whopping amount of experience coming the PCs way. (1st level's gone before you know it.) At higher levels, the experience doesn't seem to come as easy. Also, higher CR challenges are less common than in low level play, comparatively. So, leveling becomes less common.

Bearing those in mind, you can probably expect any given adventure to take the same number of sessions, but with less leveling at higher levels.