In every NA meeting they say "one is too many and a thousand is never enough."
There is no way to rationalize drug use. There isn't a way to make it ok to do sometimes. And an addict doesn't have much in the way of self control.
Trust your gut on this one. Addiction is an evil presence that will say anything to keep what it wants. and in most all cases, addiction lasts a lifetime. Even for those that are in recovery.