Yes, the oak will get ridiculous if you let it. If it's already noticeably, you should go ahead and rack off of it. It will subside a bit with age, but the experts say to oak it until it's just a little too much then rack immediately. The experts also say it's better to use less oak for a longer time than big quantities for a short amount of time. Also, the darker the toast level, the quicker it affects your drink.
There's an oak link in the Ingredients Sticky in the Recipe/Ingredients forum, not in first post but on page 1. It's got some science in it.