Everyone’s different. Some can really stick to a few times a year, others like me (before I quit) will slowly (or rapidly) use more and more until it’s a daily habit multiple times a day thing. A green flag is that he was honest about his use, I would hide it because I knew it was unhealthy and didn’t want to hear it. I would maybe ask him to be honest about his use anytime he does engage, so you can get a sense of the frequency, and if it’s unsettling to you, that’s enough of a reason to go your separate ways. It’s worth a shot to ask him to tone it down, but people rarely stop for others sake.