The situation:
If you spent your all 100 courage points you have to wait 10 minutes for 20 courage.
If you use them after 10 minutes you have again 20 courage and so you can do an attack.
If you don't use them you need a lot more time to go from courage 20 to 40 in order to do 2 attacks.
So if you want to do a lot of battles you have to attack every 10 minutes and stay in pc for hours...
The suggestion:
Courage points should be filling 20 points every 10 minutes independently of how much courage you have, with maximum courage to stay as it is at 100points.