The figure you want to kind of hold onto--my folks and I have looked at this, and we always provide this advice--is the number of rotations.
After your third rotation is when you really start thinking about whether you should stay or whether you should go. All the way up to the third rotation in anything, be it Afghanistan or the Congo, operationally, it is still part of the challenge of why you joined. After the third, it becomes a very different understanding or construct. That is why the commander of the army has in place a policy to ensure that people don't....
You'll see those who have gone on four or five. In many cases, they want to. If they want to, they'll go. But after three or four, it's your choice, and the army will step forward and support you.