Fermentation question

Started brewing about a year ago. I have about ten extract with specialty grain brews under my belt. All of these brews were done fermenting in about 7 days with consistent FG readings.
All of my brews turned out great. I keep reading about other brewers leaving their beer in the fermenter for two weeks or longer. Am I bottling too soon? If so I have not tasted anything that would indicate so. What is the advantage to aging in the fermenter if the gravity is not changing?

Thank you

basically it allows the yeast time to "clean up" after themselves. i would suggest to just try it on your next batch. leave everything in the primary for at least 3 weeks and take a gravity reading like you normally do. measure again the next day or so and bottle if the gravity is the same as the day before. let it condition at least 3 wks in the bottle (unless its a wheat beer) and try it then. you may be surprised at the improvement, you may not, but it seems to be pretty common procedure for a lot of homebrewers here.
HTH, YMMV

Funny you mention wheat beer. I have a wizenbier that seems ready for bottling. Should wheats be left to ferment longer or less?

I would ferment it just like any standard brew (set and forget for 3 weeks), but i've read that wheat beer tastes best when it is "fresh". So you could get by with less time bottle conditioning, after fermentation is complete, to get the flavor you're looking for based on that style. I'm not a huge wheat beer fan, but this seems to make sense; in that you would lose a bit of the cloudiness the longer it sits in the bottle.

I am not a big wheat fan either but my wife loves them and absolutely hates IPAs. Thanks for the advice.