Hi anjaq!
I had FFS 8 months ago with work on forehead, orbits, nose, further a complete midface lift and also chin and jaw work. Heavy surgery with cutting and stretching nerves all over the place. Cutting is inevitable in the scalp region as you mentioned before. After a few months or so the feeling came back in steps, now I'm near 90% I suppose, the feeling might be reduced a little but it's enough that it doesn't bother. Midface is a different story. Inevitable cutting in the ear region normalized about 5 months post-op, I had nerve irritation in the cheek area causing partial facial paralysis. It took around 2 months for the nerve to calm down and regain control, but since this nerve is controlling movement, no sensitivity loss was experienced. In the lower third chin was numb for two months.
Nerves recover fully most of the time if they are just irritated (like stretched or similar), if they are separated chances might be better in zones were the nerve tissue is dense (like face). Nerves are growing slowly and they have to connect with the other side which can be tricky. Sometimes a "neighbour" nerve can do the work for the damaged one.
To make the long story short - I feel fully recovered after 8 months, like >90%, but for sure I'm still in the healing process. The benefit of FFS in my case exceeds by far the potential risk of permanent nerve damage, even if my case is a difficult one because of adverse skull preconditions.