Given the psychology of addiction, is it reasonable to expect an addict who's seriously jonesing for a hit to be this cautious and delay the satisfaction of getting high?
I dont see how there is a difference to not sharing needles. The addiction argument is the same there and even people at the end of their line managed to follow that rule during the periods in history where the war on drugs included syringes as drug paraphernalia. Its simply not an option to break that rule. No ifs or buts.