We could also use frequency of use and settings as alternative (which might legally increase by age). Personally I don't let people smoke with me till they are 27 or so, which is somewhat ageist, but I accept them if they bring their own stuff before (tolerate, but not enable).
I don't think something magical happens at 25 like a light switch but we still gotta choose some age as a limit
Do we need to though?
We could also use frequency of use and settings as alternative (which might legally increase by age). Personally I don't let people smoke with me till they are 27 or so, which is somewhat ageist, but I accept them if they bring their own stuff before (tolerate, but not enable).