Couple of things:
1. You will need to describe the off-flavor
2. I've had beers in Primary for much longer than this without any off-flavors.
Likely the off-flavors aren't from being with the yeast for too long. However, that doesn't mean that the off-flavor isn't from your yeast.
Once you describe the off-flavor a little more, then maybe we can help you.
"There is no strong beer, only weak men"
"Pretty women make us BUY beer, ugly women make us DRINK beer" - Al Bundy
"Give a man a beer, he'll drink for a day. Teach a man to brew, he'll be drunk for the rest of his life."
Primary: Hoppy Wheat, Porter
Kegged: Reaper's English Mild (OO), BBK Jr., Lagunitas IPA, Fireman's #4
Notable Empties: Oaked Black IIPA, BBK I, Red IIPA, Burning Bush, Apophis "The Destroyer", Vanilla Porter
On-Deck: The Titan BW, Ale of Olympus