> Pretty sure the Romans thought history began with the founding of their city. Which they dated somewhere around 750 BC. Before that was just myth and legend or something. How seriously they took their myths and legends I don't know.

Well, even the founding of Rome was tied up in more myth than history, so it's probably pretty hard to disentangle how seriously they took any kind of history. But the idea of the Earth having existed essentially unchanged forever wasn't uncommon in the ancient world, so I wouldn't be surprised if that was the general attitude.

> The longest lasting "stagnant" kingdom from actual history I can name off the top of my head was probably ancient Egypt. If you count all the dynasties going back to the very beginning of recorded history, the various Egyptian kingdoms lasted for about 3000 years, with one or two gaps or interregnums or whatever they're called (can't be bothered to look it up.) That's 3000 years with approximately the same level of technology. Fantasy novels think nothing of doing this two, three, four, or even five times better.

It doesn't help that the Egyptians measured years in terms of the reigns of the various Pharaohs (the seventh year of the reign of Atenatep, for example), and many of these reigns overlapped, so estimates of the total length of the Dynastic period vary by several centuries.