I remember in class we were learning / practicing what you say when you meet up with another person after a long time. some one said «ah! ça fait longtemps qu’on ne se pas vu! Je suis excité…». they were corrected on that by the teacher.

I might be getting some of that phrasing wrong. my ability to write French is slowly degrading (I can speak it well enough, but not as well a a few years ago)