Agree. It must be, "I've known him for years".
Let me add some more verbs which cannot be used in progressive forms:
hate, want, wish, desire, see, hear, feel, notice, understand, remember, forget, believe, recognize, appear, possess, contain, consist, etc.
By the way, Mister Micawber, I wonder if the verb wonder may be used in progressive. Can I say, "I am (was) wondering if this phrase is (was) acceptable"? It is a progressive form here, isn't it? I have seen such constructions before but I am not sure they are correct (in BrE).