Things HAVE improved a lot for me.
There that's the positive bit.
I don't want to forget that part of the original question.

I have had Post-concussion syndrome for just over 18 months now. And I still have symptoms on a daily basis. So that doesn't sound too hopeful. However, if I caste my mind back to a year ago and what I was doing and feeling like a year ago, I am tons better.

I have kept an accident diary. Mostly I got bored with it because each day is pretty much the same as the last in the catalogue of symptoms. However, it is good to note when you do something for the first time and you see that you must be recovering.

I felt really dizzy for 3 -4 months, but that gradually improved to the point where I started driving again. For the first 6 months, it felt strange to walk as if I couldn't naturally direct myself in a straight line. At 18 months walking seems pretty much back to normal. At 6 months, I tried to go on a run. It felt really strange. This morning I went on a run and it felt pretty normal. I am really unfit now after 18 months of not taking much excercise but I was tired out in a normal way not a concussed way. After 6 months I felt that I could go swimming again. It felt strange at first but soon improved.

The biggest improvement that I remember was that after about 7 months I actually something. Before that I was constantly in some degree of pain or discomfort. I remember being asked if I had enjoyed going on a walk, but walking along the beach in the sun is hard to really enjoy if you have a headache and feel ill. But after about 7 months my discomfort was low enough that I could enjoy things.

So, I guess that's the good news: it is possible to improve. Things can get better.

However, if you were ask me if I feel completely better, then the answer is no. If an uninjured person woke up feeling like I do, I'm sure they would feel quite justified in calling in sick from work. But just because the symptoms haven't completely gone doesn't mean that you aren't getting better, slowly....more slowly than anyone would want, but there it is.
If I compare today with yesterday or even last week or a month ago, I don't see an improvement. However, if I go back a year, then sure I can see that I am actually getting better.

I am starting a new part-time job next week, so if that works out that will be another step in the right direction. The last neurologist that I saw said that my condition would settle down in 1 to 3 years. I could be on track for that. But I don't think that doctors, even neurologists, know beans about the condition. You could be better off getting the responses of people who have gone through the same thing, even though I'm sure that all injuries are different and everyone responds differently.

So, I hope that that might help someone to look on the bright side, even though, let's face it, the condition is really pretty bad; it can still improve.

I'm going to try variious treatments, one at a time, and see if they help.
They are acupuncture, craniosacral therapy, neurotherapy and amitripyline.
So, I would be particularly interested to know if anyone has tried any of these and how they got on.

Wishing you all the best or at least better health.