I used two vanilla beans when I transferred into secondary. I left it in secondary for about a month, and the vanilla character completely dissapeared. It took all the roasty goodness from my porter too. It was a nice beer after it aged, albeit a little weird. Somewhat like Sam Adams black lager.
I recommend adding the vanilla beans no more than a week before bottling. That's when it smelled the best.
Allergy Warning: This post was made by a person who may be nuts
From the store: Nothing right now, how sad
Up Next: Thinking about an amber rye
Secondary: "Not as Pale as Death" pale ale (since april, man I hate bottling.)
In bottles: Lager than Life Beer, Rocky Raccoon Honey Lager, A nameless Imperial Stout (my first AG!)