border management and defenses - do you use them? up to what value?

[Master Shake]

The benefit of not having to pay upkeep on the PD is huge. Army upkeep can eat up 80%+ of your income every turn.

Having a real army defend in a province with decent PD is a great asset. I ususally design my unit set up to incoporate the start location of PD units. I leave a gap in hold/attack troops in the center so that the PD cannon fodder can charge out quickly. I want those free infantry units to take the first wave of attacks and spells.

The AI also takes PD into account when deciding who to declare war on and attack. If you have lots of low-PD provinces, good chance you could be the next target.