Adding flavor extracts at bottling or in secondary?

I will be brewing an imperial nut brown in the next couple weeks and will be adding hazelnut and vanilla to it. Is it better to add the extracts at bottling, or into secondary and rack the beer on top it. I always leave my beer in primary for 21 days and then bottle. If I decide to rack to seconday how long should I leave it before bottling? Thanks!!

I would say it depends on what you are useing. If it is powdered or in a liquid form, I would say at bottleing. If useing whole or chunked hazelnuts and vanilla bean(s), a secondary would be more adventagous. It basically comes down to amont of exsposure time. With liqiud exstracts you dont need any time for flavor to seep out. Where if useing solids you need about a week useally for good flavor profile.

i used whole thawed blueberries and the color was great. the smell was faint and i could barely taste them. 2 1/2 lbs. in a secondary for a week. i heard a guy put some liquid extract in his keg upon kegging and it was great. if ya bottle i would say go a little heavy at first in the secondary. the yeast will probably get a second fermentation going and i was surprised how much flavor was lost with 2 1/2 lbs of berries. next time i will puree it and use more but still keep the time to 1 week and see what happens.