Well, he could get copies of PihKAL and TihKAL and go through the list, one at a time. That would occupy him for a few months...
As for his hardiness, he probably takes or took drugs every day, but not in heroic doses, not every day. His reputation is probably bigger than his actual habits.
In the excerpts from his book I have read he says that he had more control than most people when it came to drugs. The way he put it was that he was only looking to get high and not more high. Basically he would do coke at the beginning of the night and not keep doing it all night like others.