Not to often because all four of them act like lunatics
when they get it.
They prefer to roll around in it as to eat it. They are
also very picky about the catnip they like. They DO NOT
like store bought nip. I have a friend who found some
heirloom cat nip plants and grows it for her 11 cats, so
she gives me a large mass of it in the summers.
My furkids loves the fresh from the garden nip.