Looking for tips from the pros

[Endoperez]

It's good if you're going to fight a lot in that province, and keep on winning. Human players probably won't assault it many times with forces that aren't good enough to beat you. If it's a chokepoint, go for it. If it's not, he'll go around it. If he goes around it, or you take a few provinces and the front of the war moves, you can't move the PD elsewhere.

For some nations, it's worth the money, but it's always situational.