Is the high similar to heroin/morphine etc in humans? Because if it is, then is catnip not addictive to a cat? What if a cat discovers whole fields of the stuff and decided to revel in it until death? It's unlikely but it could happen
Anecdotr: one of our cats, upon presented with unlimited amounts of catnip, consumed it until it became basically K-holed and then refused to touch the stuff for a few years afterwards, suggesting the equivalent of a hangover.
Also, from the article: "Big or small, the felines surrendered to the substance, rubbing their heads and bodies in the patches for an average of 10 minutes"