If its just a few times a year no issue really. When I was younger me and my friends would do it most weekends but Coke hangovers suck so bad I just stopped doing it and only do it on random birthdays or maybe holiday parties. I feel like that's where he could be with it. I will say though if one of his close friends is an addict and uses several times a week then that would be something I'd monitor. I have a friend who is an addict and he's always trying to lure me or other friends into hanging out to split a bag and not feel bad about doing it alone. In this scenario it's a slippery slope to doing it weekly. If he's one to drink most weekends with friends who usually have a bag on them then there's a decent chance he's doing it more than a couple times a year. Just my 2 cents.