The "no down time" thing is right on. My old Army National Guard buddies are going on their 2nd or 3rd deployment. Their last one was guarding a prison, even tho they were artillery qualified. They had the stress of deployment, guarding prisoners, and daily mortaring to deal with.
I read that the improved communications deployed military are enjoying (email, video teleconference, etc) also adds to stress. They know the issues their family deals with daily, instead of getting a letter every once in a while.