Well, it dind't quite work all that well in practice. The nomads' most common foes were other nomads, who had all the same advantages, and the Russians, Byzantines, Chinese et all developed long-range cavalry raids, surprise night attacks on camps, converging column strategies etc. to fairly proficient levels to keep their grazing and troublesome neighbors in check.

'Course, two of the three in particular had serious problems with this "quality maintenance" thing, especially as far as central adminstration went, but that's a different story...