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

No! You either lost your mind or you are still young and naive enough that you are still eating your boogers. Not worth the risk, please don't try it. Miley cirus has millions at her disposal and dr. Drew on speed dial. I'm pretty sure you don't...
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.