It's a fairly complex question. It's like asking how much should my daily running volume be? The answer (or guidelines) can't really be given unless we know whether your talking about intensive tempo, acceleration development, speed endurance, etc. For your question, we need to know what type of plyos you're speaking of, what the prior experience is with plyos, what other training means are being employed, etc.
My Army guys can hardly handle any hard plyo work. We do under 250 high intensity foot contacts (box jumps, hurdle hops, bounding, etc) per year because they simply can't handle the added stress.