One of the main reasons the older mantra was to get out of primary ASAP was that autolysis might happen. But with the beer community, folks started finding that even weeks on end....they weren't getting autolysis.
I actually think the yeast autolysis might have had merit at one time...several decades ago. Remember back even before 78 the amount of yeast available to hobbyists were very limited, and were usually dry cakes.
If you've heard some of the interview with the oldtimers on basci brewing, they talk about the yeasts being very old and cakey, and not very good to begin with...
Like Palmer says as long as the yeast is HEALTHY several months on the yeastcake is OK...but back then the yeast may have not been very healthy to begin with. It could have been several months or years old with a very low viability.
And they did notice autloysis in their beers.
And Papazian was writing his book from right around that time period, when yeasts cake in dry cakes and may not have even been stored properly, and many people just placed towels and cookie sheets on their ceramic crock pot fermenters.
So he and his contemporaries influence the knowledgbase back then just like we affect and alter the brewing culture today with these ideas.
This is an ever evolving hobby...Places like this is where you find the most state of the art information/wisdom about brewing, because of the sheer number of us trying new things, hearing new things, and even breaking new ground and contributing to the body of info on the hobby...Look at some of that inventions that came out of here, and then ended up later in BYO articles by our members...
It's just a shift in the culture, it doesn't mean that beer won't be made either way...someday some enterprising brewer from here or using forums as a reference is going to write the NEXT brewing bible, and talk about long primary. and it' gonna be "beery canon" for a number of years, or it will end up as an article in Zymurgy or BYO, and people on places like this will be quoting from that for awhile...then the culture will shift from that idea...
Heck even the last update of Papazian was 7 years ago. Just think of all the technological changes in the last 7 years, and you'll realize that knowledge doesn't exist in a vacuum....Just look at this place....the "culture" and ideas shifts over time...like I said, places like this, we, you and me and everyone else here, are the cutting edge of brewing....
Those of us who opt for the long secondary usually do it because of what we have read, but mostly because we have noticed an improvement in our beers from other methods.
I joined the long primary camp, precisely because of my contest scores last summer....I kept getting feedback and higher scores for the beers that long primaried....They were described as "jewell like" and "crisp and clean tasting."
As opposed to the beers that I entered using the more traditional means. I mean I had some of the same recipes I brewed that overlapped, like my amber ale, and Dead guy clones, and I could tell that the version 2's of my batches, the longer primary tasted and looked much better....