hmm okay trying to unpack what your saying. So culture, peoples acceptance of the system and the form of government aren't relevant to how long an imperial dynastic system can last? These are relevant and also is stable borders which I sorta mentioned with the wall.
There has to be some form of acceptance on the governed for the system to have lasted as long as it did. Look at feudal europe, the Kings authority came from the pope who in turn got their authority from god. For a long time in history people have accepted the idea of divine rulership. Also there has to have been some sort of mechanism of governance that keep the people in line somehow. Whether is be standing armies and/or educated bureaucrats governing the people in the towns and states.
As for isolation, yes and no. China did trade with it's neighbour and the the west (middle east, silk road), but the were not threatened by the west (as in Europe) for a long time. The only threats where from the Kingdom of Korea, Manchuria, Mongolia, Japan and nations to the south. I don't remember the nations bordering the west of china being a threat. Also China build the great wall to protect them from the North to give them border security. They didn't build a wall the south so they weren't as big of a problem as the north was. Also i think China has only been successfully overrun twice. First by the Mongolians when Genghis Khan overthrew the current government and his son later established Kublai Khan later established the Yuan Dynasty. Also secondly with the Manchurians getting in via the backdoor and overthrowing the Ming Dynasty and establishing the Qing Dynasty. (If there were other foreign powers that successfully established themselves as dynastic rules before 1911, let me know.)All the other Dynasty changes/overthrows have been internal.
So if external borders aren't as much of a problem for a sovereign state then a state can turn itself inwards and govern its subjects effective or attempt to. Also this would of allowed for greater trading inside the country to keep the populace happy. Usually when there was a change in Dynasty, it was internal (not foreign invaders), but i guess it took a long time per dynasty for it reach critical mass where the sovereign effectively lost control. Corrupt rulers, ineffective armies, popular revolt by the people, Believing the emperor has lost the will of heaven.
Also when a Dynasty was overthrown, it didn't get replaced with a new form of government, it got replaced with another Dynasty governing the same way. Imperial emperor etc etc. Essentially they replace the former government with the same form of government with the emperor having absolute power. They didn't replace it with any other form of government. To the Chinese, this was the best sort of government. Also their peers (other nations) also employed this sort of governance. An anecdote, i watched this on some docu channel, but when Imperial Japan lost ww2 and the US administrators had to write up a new constitution. They got the Japanese officials to write up a new one, but they wrote it up exactly as it was before the war giving the emperor absolute power. Eventually the US administrators wrote up the constitution themselves. The point is that the people were ingrained with the idea that Imperial emperors was the best way to govern, so when a change of government is meant to happen, they just reinstall the same sort of government. Or to use a pop culture comparison. In ME2 When you talk to legion after you reject the reaper tech, he mentions something that if you had accepted reaper tech it would of forced humanity and its technology to develop along certain lines dictated by the reapers. The same can be said for a political system, once it's entrenched and is running for a long time it becomes alot harder to change course. Obviously it can be done, one just needs to look a Europe but it's difficult. Also the intellectuals of China were not advocating a new and different form of government like the ones in europe did (eg Locke, Rights of Man after french revolution), they were just advocating the same type of government with a benevolent ruler. Not a new system.
TLDR; China has fairly stable borders most of time. This enabled more effort to be put into internal control and create stability (enforced or harmonious). Standing armies, trading, bureaucrats. Whenever there was a new dynasty, they just governed like the old. The mechanisms of government and thinking on how to govern didn't change much. Chinese intellectuals didn't advocate new forms of government, just the same type with benevolent rules. The idea of the divine ruler ruling with the Mandate of Heaven. There was no Locke advocating a new form of the social contract in government theory.
. During the Warring States Period and the early Han Dynasty, China grew greatly and the need arose for a solid and centralized cadre of government officers able to read and write administrative papers. As a result, Confucianism was promoted by the emperor and the men its doctrines produced became an effective counter to the remaining feudal aristocrats who threatened the unity of the imperial state." (http://en.wikipedia.org/wiki/Confusianism)