Amen.
I am a yeast biologist, but not an expert on brewing science (we use yeast for different purposes than brewing). But, what I know tells me:
-you'd need a TLC (thin layer chromotography), or, better yet, an HPLC/MS machine to really quantify the difference between 10 days and 4 weeks. But, unless you are in a field like I am, you don't have access to $500,000 instruments, and, even if you do, you aren't going to waste your time unless you're a scientist for a megabrewery. So all of the evidence we have on our own brews is anecdotal.
-I absolutely positively guarantee that any beer that sits in the primary for 4 weeks is going to be different from 10 days. Not only is there a big genetic variation among the yeast (simply due to statistics-- trillions of cells!) which is going to cause unique variations among various small byproducts-some yeast are going to be slow, some fast. Even if the yeast are mostly inactive, they are still alive, and will do whatever they can to survive until the beer is unsurvivable. There are also spontaneous chemical reactions that occur, and they will have gone further at 4 weeks than 10 days. (Many of these same reactions will also occur in the bottle too, but not all of them)
But, here is the important part: some of you will prefer the taste of a given brew after 10 days in the fermenter, or even less, while others like the way it tastes after 4 weeks. I bet a bunch of us (myself probably included) can't taste the difference. So this entire argument is moot.
The only thing that does matter is the question: "X is wrong with my beer, how do I fix it next time" and whether the time on the primary is one of the answers.