It is a bit misleading to say that the Yellow Turban Rebellion took 21 years to suppress. It started out as a religious movement and then became a widespread rebellion organised by its leader Zhang Jue in March 184. Though they had some initial successes, the tide started turning soon enough as the government started organising a response, and when Han forces recaptured their stronghold of Wan city on 11 January 185, the Yellow Turbans were effectively ended as a political force after about 10 months in rebellion. Sure, some scattered remnants still remained, but these were essentially local disturbances that could be mopped up by local authorities.

True, several groups show up later that are also called Yellow Turbans, but it is far from clear that these had any direct connection to the original Yellow Turbans and their beliefs.

The Yellow Turban severly shook the Han emprie's hold on its provinces, and a general rise in unrest, banditry and lawlessness was the result, but unlike the Yellow Turbans they were not united in a common conspiracy against the Han state