Weigh your chips and keep track of how much and how long they are in with the beer for future reference. A good practice it to reserve some of the beer (or wine or cider) un-oaked so if you get too much oak/whiskey character you can blend to the the taste you are looking for. My experience has been that you'll have to add MORE whiskey to the beer, but over oaking can be a problem depending how much you use.