Thinking about tribal and nomadic societies, this idea came to me:
Could a relatively advanced society exist, that would still be nomadic?
(Relatively advanced in the medieval sense; moving a smithy or a foundary does not sound exactly like fun, right?)
Such a society would have to exist because of pressing, hard-to-avoid reasons:
The land gives little support
This country has likely no access to the sea, so no easy fishing. The land is not very fertile. To make at least some settlements possible, "fresh land" would offer some harvest, but already the second year would be less productive, the third hopeless. Simply dividing the land into three or four parts would not be enough, as it would regenerate too slowly (let's say 10-15 years). Maybe the only vegetable/fruit/crop that can feed enough people is too taxing on the land. If hunting is a substitute, after a few years the game would be also too scarce. And once the relatively good land is exhausted, it is time to move on.
While it is likely the advanced technologies were imported from elsewhere, the whole place is probably separated from a "true" civilisation. For instance, food cannot be easily imported, and better agriculture may be already known elsewhere. Alternatively, in these barren lands may begin the civilisation itself, the whole world being behind in development.
Disease and Vermin
A high concentration of people depletes resources, but attracts other things. If the sanitary systems are lacking, or somehow diseases always catch on after a few years, then better let's go! Insects may be a similar hindrance.
Uncomfortable traditions tend to become forgotten. But if from other reasons it is necessary to be a nomad, a nice tradition can supply honour and even hope to those depressive moments, when you abandon what you have built and achieved, and can only hope your new/old home will be still standing. Legends and promises of deities can also work here.
Summary and random thoughts:
A not very friendly or fertile land, maybe a plateau high in the mountains. There exist probably several "cities" for a community, but only one is occupied at a time. The others are left behind empty, closed as possible against animals and vermin, guards are sent occasionally come here, or small outposts can guard them. Ever found a completely deserted city, that seems to be left only days/weeks ago?
Being always a bit on the move, a very pragmatic view rules this society. What you can take with you on the "Big Move", is always limited. The society would be based strongly on families, as only a family can own a house in each of the cities. Laws, or at least strong traditions control property rights, so no one can occupy the house of someone else. And having no family is a terrible fate,
These "cycles" probably control much of their life. Once the Moving into an old city is done, festivities would start, excellent for weddings and having children.
Hunters/Warriors have several important roles: first kill the vermin that "takes over" any abandoned city very soon, then feed the population, and possibly defend them from the vermin they attract later. And if someone turns up at the wrong place ("Hey, look! An empty town we can settle in!"), they have still more to do...
Final Note: this setting and its moving nature is not likely to last forever (as advances in technology or magic will break it), but could certainly surprise travelling adventurers. A possible step between the nomadic and settled society.
Please be aware that this is just an experiment on: A and B seem to exclude themseleves, how would it look if not?