Some say that the symptoms you have at one year are permanent. There is evidence that recovery can continue many years later.

There are a few issues that confuse this;

Many of the so-called 'fully recovered' do not notice lingering symptoms until some event triggers them. Then they often do not relate the new or relapse of symptoms to the original injury.

Many get to the point of reluctant acceptance of their prolonged symptoms and drop out of the medical treatment system thus appearing to be fully recovered.

Many symptoms are overcome by learning new ways to do things. Others are overcome by changes in lifestyle/behavior.

It might be better to phrase the question into a context such as, When do you need to accept your symptoms as prolonged or permanent so as to apply for disability, settle litigation, adapt to a new way of living, etc.?

My history goes back 40+ years. I have declined in steps over the years. Some symptoms resolved in the first year. Others became 'dormant' to return when triggered. The more concussions or even very mild traumas my brain has endured, the more residual symptoms I have had to learn to live with. Some of my symptoms and behaviors I did not connect to my concussion history until the last 12 years even though I now believe they were caused by injuries decades ago.

So, there is not single, easy answer.

Do you have a context to relate your question to?

My best to you.