??? I was told that most kittens less than 6 months do not react to catnip, and to avoid having it in toys for kittens for fear they would acclimatize to it. Some cats never acquire a taste for it.

And I try to limit Cassy and Livvy to once a week or less because they seem to have lower reactions to it when it's too common.

But, no, for adult cats I haven't heard of anything like you were told. What a mystery!