I am also playing ironman and won every war and defending a couple of jihads so far, but I can not do it as fast as before. You cannot pick your enemy if you are defending, or if someone declares a jihad on your realm, for example.
Waiting for an army is a way of wasting time actually. The time you are waiting for an attack, you must have the troops ready. And this leads me to the next point:
I need to chase them because I want to end it quickly. What happens if while I am waiting for a next wave of my current adventurer war, some other declares war on me and I have to defend against two?
This is, indeed, something I usually do when I want to debilitate an enemy. I sometimes check if he is facing and adventurer, and press my claims there so he had to split armies to both. I don't want that happened to me.
By the way, if someone wants to roleplay the game, shattered retreat of thousands of miles should be completely discarded. And even more, I don't beleive that any real medieval lord facing a real adventurer and with a defeated army in his realm would wait for an attack to his levies army, instead of trying to solve the thing once and forever.