Is hookah safe to do if its only done every blue moon?

Hmm good question: Nicotine is one of the most addictive substances, about 1/3 of people who ever use it become addicted, 33 percent. It's about 25 percent for heroin, 10-15 percent for alcohol. So by definition, if you become addicted you will no longer have control if it's once in a blue moon or not, you will do it more and more and more.Not sure that is a risk worth taking.

Should be fine: Blue moon is the occasional event when the dark (new) moon is present twice in one calendar month - a very infrequent event. You can do hookah on that schedule with no ill effects.