Are crazy people crazy forever?

I dated this boy for a few weeks about half a year ago and he turned out to be kinda crazy. Like, after I broke up with him (due to being smothered and pestered by unwanted ‘i love yous’ and a tendency to become an asshole when sexually intimate) he threatened to kill himself and did a lot of immature, cruel shit to me. Now, I’ve recently gotten back in touch with him, remebering why I liked him in the first place (great sense of humor, weird, adorably socially awkward, etc) and he doesn’t seem to be showing any signs of craziness. But he also didnt seem crazy in the beginning of the first time around. Is it possible, though, that he’s changed and isn’t crazy? Or once a crazy always a crazy? Help. I would like to have some thoughts on this before I get in too deep.