I want my dukes to hold as much of their duchy as possible. And not one county outside it.
My thinking is this makes it easier for them to upgrade castles. A few counties is enough income to actually afford the upper level improvements. If they have one castle, upgrades are slower. In theory, it shouldn't matter -- X income time X castles ought to break out the same. But in practice, it seems to make a noticeable difference. Plus they do a better job rebel bashing. And I don't want my vassals weak and fighting each other. If they revolt, they're all going to do it in a big group anyway so it doesn't really matter. I want them strong enough to give me lots of levies so I can bash Mongols and Aztecs.
