I'm a year post-concussion this Sunday and still improving, in fact faster than ever.

I recently read about a study on long term stroke patients, one of whom saw improvements from an intervention 50 years after their stroke. Stroke patients are often told similar things to us in terms of "after X months you won't get better anymore", but the brain goes on being plastic and can learn new things throughout life even after an injury.

So ignore these people who are trying to sound like they know more than they do and keep on going. There's more useful advice on this forum than they could give you anyway.