How long will it take to "get better" after a traumatic brain injury?

Upto 9 months: Initial improvements might take upto 9 months even after that might require further group rehabilitation.

Depends on how bad: Not all tbi's are the same, see: http://cpancf.Com/headinjuryclassification.Asp mild concussoions recover quickly, and while more severe injuries show some noticeable recovery during a 3-9 month period, some less noticeable recovery can continue for longer. In more severe injuries a two year mark is commonly considered a point of maximum improvement, though I have seen some small gains after tha.

Depends on injury: This depends on a number of things, namely: the severity of injury, the condition of the patient before the injury, any complications due to the injury or after the injury. There are also different definitions of "getting better." that being said, usually the highest rate of recovery occurs during the first few months, then the recovery usually still climbs, but approaches an asymptote.

Up to one year: It can take up to one year or more to recover