Would it make sense to occasionally sprinkle in 3-volume APs amongst the usual 6-volume ones?
If you look through the messageboard posts on the individual books, it seems volumes 5 & 6 just dont get as much play. Mummys mask book 5 has just 21 posts. And book 6 has only 13. This leads me to think that a lot of people start APs but rarely get to the ends of them.
If paizo were to insert shorter APs of 3 books in length. They could cover more of the world, they could start these at different levels. And not every story would have to be epic.
I just finished a 4 year campaign of rise of the runelords and the thought of another 4-year investment in a new AP is a bit daunting. But maybe just a 3-book series would be more reasonable.
This has come up a lot over the years (although not for a little while, I think).
There are a couple of reasons commonly cited for why 3-part APs are unlikely:
The first is that the first and last episodes of an AP are the ones which take the most work. Groundwork needs to be laid and loose-ends need to be neatly tied up. That means that producing two three-part APs is considerably more work than one six-part AP. Hence there is a limit imposed by staff time and other such resources.
Another is a natural conservatism when it comes to Paizo's flagship product (which the APs used to be and which I presume they still are). The company has done very well over the last several years based in large part on the success of the "two six-part APs per year" model. Whilst it is likely that deviating from that wouldn't be calamitous, the more and more central to one's operations something is, the greater the risk with tinkering with it. The AP subscription used to be described as "what keeps the lights on and pays the wages" - now that's probably changed somewhat over the years, but I suspect it's still a really important part of their business model. As such, the risk of it tanking for a year or two, even if minuscule, has the potential to do significant damage to the business in terms of cash-flow, profitability, certainty, etcetera.
At one point, I heard the idea mooted that if they were to try tinkering with the AP model it would likely be in a far less significant way - something like trying a five-part AP and a seven-part AP one year or something (there are also people who feel APs are too short, so this would have the advantage of keeping more customers happy - plus the people who want longer APs are less likely to cancel in the face of a single 5-part AP than they would be if they saw a couple of 3-part APs come onto the schedule.