To see that all it takes to let the time flow while you stand in one place. They go on their own business, capture buildings, attack each other, heal, buy/sell trophies, exchange their characters for better ones if units in castles upgrade faster. Waiting might be a good option on an easy level (troops in castle will upgrade relatively fast) and then you can take on the enemies. However, waiting too much on the ultra difficult level most likely will lead to a situation where enemies get too strong and you won't be able to do anything against it.
That sounds pretty good, I dream of a game with such settings, and with more emergent world ushing this concept further from space rangers, if you want an inspiration you should definitely check it. But that maybe for a next game if you could tell me if that could work:
-Different factions controlled by AI with different diplomatic relationships, that all play, and try to get stronger. It could also generate quest to do.
-maybe some outside danger, sudden monster awakening, and you among other mercenaries would help kingdoms independent villages/castes.
-you could discover ancient technology, and spells that would help kingdoms with farming, you would have to invest to develop them, you could then give them for free to make kingdoms stronger, and better diplomatic relationship with them, or sell them.
-you could do diplomatic work as well, or be a merchant, make money, and gain influence that way, for example independent castle in the new situation with monsters swarming the kingdom could be tempted to join bigger kingdom, there could also be independent races that could join, and each fraction could specialize some could be more technically advanced some better at alchemy, some in other sconces etc. after new race would join it would depend on kingdom specialty into who they could be trained. For example big strong race would do best with somebody with strong classic military, and that are proficient blacksmith, while smaller intelligent race would be good for mages, or science based kingdom. (maybe a steam punk settings to have all of that variety)
Also just because monsters are invading it doesn't mean that everybody is united, some kingdoms could underestimate it, and see it as just an good opportunity to gain more cities, and mines, some would have bad history with other kingdoms. Some could be stubbornly neutral, like dwarfs who only want to sell they weapons, and get mines, and who try to close themselves in they fortresses. You could use diplomacy/prove your worth to them or that danger is too big, and threatens them all would of course require some real action not just your world.
Ultimately somebody would have to solve problems with monsters, figure out the cause, and destroy they source of power, they could also take over cities, and turn people into monsters there, but that process could take some time so the sooner it would solved the better, other merc, and kingdoms could try to do it depending on they situation. The ending either everybody gets overrun or somebody solves the problems, not necessary you, but you could still play important not direct role, or direct depending how you prefer to play, or what made more sense.
T Cursed Castle scenario has also time limitation, it's pretty big but there is one nevertheless.
That is fine I don't like a default limit as much as a living world that you have to take into account at all times, and that gives you instant feedback.
While I disagree about some of the things, it's still good the preview is up there. And I wish it was done by a writer who previewed PoE... We are the Euro Truck Simulator of RPGs 
