I was scrolling through the banners out of curiosity earlier tonight, and it seems like a lot of them have different requirements with about the same type of theme (like one that you get for extending your lifespan beyond 80 years, and one you get for getting it below 50 years.)
It makes me curious; are there banners that you could be locked out of attaining forever, or could one single Nation collect them all? (Provides that they have to rapidly change policy all the time to get every single banner.)