Really? I was told by many to leave it 4 weeks in primary. I do 3 until I feel the need to change.
I've never gone 4 weeks, as I don't see the need. If the beer is at FG and has been for a week or so, and the beer is clear, then why wait? I mean, sure the whole "yeast cleaning up after itself" is a valid theory, but it certainly doesn't take weeks and weeks- more like 48 hours after FG is reached at the most. Once the beer is clear, and has been at FG for at least 5 days, nothing "magical" happens in the fermenter.
I believe strongly that a well made beer (proper yeast pitching amounts, proper temperature control, proper ingredients) won't create a ton of flavors in the first place that need time to "clean up" (aside from diacetyl and acetaldehyde). Some beers, like my oatmeal stout, DO need a bit longer for the flavors to meld but that can happen in the keg/bottle. Two weeks is still plenty of time in my opinion.
I also have seen a few brewpubs that use extract. It's more expensive to purchase extract, BUT the equipment is cheaper. No MLT, no HLT, etc. So, the cost savings at first can be significant.
I've had some excellent extract beers, and some awful AG beers. A good brewer can make an excellent beer out of AG or extract. But in my experience, there is a bit of a different in taste between AG and extract. Not bad- I'm not saying that extract doesn't taste really good if in a well made beer. But it IS different.
That reminds me of an analogy I use often. I make spaghetti sauce lots of different ways, depending on how much time I have. I also make beer.
To my mind:
Hunts spaghetti sauce in a can = Cooper's prehopped kits
Jarred sauce with adding stuff = extract kit
Homemade sauce, starting with canned tomato sauce/paste= partial mash
Homemade sauce, starting with fresh tomatoes= AG brewing
Now, you can make some pretty good spaghetti sauce with canned tomato paste and your own seasoning, and it can be better than people who start with whole tomatoes and make it from there. But the best sauce is always made by the best sauce maker, and it's rarely from the canned stuff.
Same with beer. The best brewer can make an excellent beer with extract and partial mash. But usually, there IS a difference that is noticeable. That's not a bad thing, it just is.