I think it depends on your symptoms and what part of your brain was affected by the TBI. If you get headaches, dizziness or other symptoms consistent with overstimulation I would suggest backing off a bit.

My symptoms were cognitive deficits, poor short term memory, poor executive functioning and problems with recall. For me a couple hours on the computer was helpful, helping me by remembering passwords, through email making connections with past events, and other tasks that improve memory. I'm not a gamer so I didn't initiate activities likely to cause overstimulation. I also felt the need for more social interaction so email was helped.

If you are seeing a neuropsychologist, or speech or occupational therapist I would describe your computer usage to them to get their assessment. All brain injuries are different and what is helpful for someone may be detrimental to another.