you're forgetting the viking era
that's medieval
I would prefer for the earlier eras to last longer, historically the closer we get to now, the shorter the eras get
but I hate antiquity, its terribly boring and long, I'd rather just skip that and go into the next era (which would realistically have to be chaotic and all of the sudden, the dark ages didn't just happen because it had to, the fall of Rome and the chaos that followed along with the migration period and spread of new religions are all triggers of the medieval era.
medieval is also an Europe only thing too, the whole world shouldn't be in the dark ages because Europe is)