In my experience this can depend on alot of factors and there is no right answer. I've found that the closer you are to the brewhouse (or in it) the more frequent caustic you need; closer to finished beer (bright tanks) needs more frequent acid. Extended storage tanks (like serving tanks in a pub or kegs) need alot of acid. Acid and caustic every cycle sounds like overkill to me, but it can't hurt if you've got the manpower and the chemicals.
Evolution Craft Brewing Company