Really? I use advanced world gen so...I've tried both limited site cap and infinite site cap, infinite population, etc.
Before, my hamlets and towns would only have 25-100 pop. I don't know if changing the value in the entity file actually had an effect. I haven't really played vanilla and when I did, I usually did quick world gen at max years (I forgot value) with low savagery, etc. I never got battles that had tens of thousands.
But anyways, in my modded DF, battles of 100k+ vs 100k+ were pretty common so I was happy.
That aside, I was more concerned with the legends viewer. I rely on that app to view history and map more than ingame.
Also, when I generate my world, it takes an eternity once it passes 2000 years. Its not like I haven't read suggestions to lessen the generation time but I prefer to have an older world with more history.
But that's not the problem I have. As history goes on, more and more characters, events, sites, etc are being added (assuming that as the world continues living during fortress mode in future releases) so wouldn't it eventually reach a point where I have to go and start anew?
I don't know much about the average lifespan of a fortress but most of my recent forts make it past the first century with few problems.
Naturally, the feature for interaction with the outer world will become a feature in the distant future but I'm still a little concerned.
Put me at ease.