When units come and go together, it helps with the PTSD. I think cohesion and moral support stays intact and greatly facilitates integration back into civilization. In Nam, we rotated in individually though in the early years, divisions/brigades etc entered as whole units. We left individually and psychologically alone. when I got on the freedom bird home, I didn't know a man on the plane. We were all about 14 hours from civilization thinking life would be so great and wonderful once out Viet Nam. We had visions of hamburgers, cold beer and round-eyed women - we had lost all contact with civilization and were going home. The guy I sat beside told me he was being dishcharged and would be a civilian the next day. when the plane took off, he got a blanket, covered his head and sat and talked to himself all the way to Okinawa. Nobody had a clue what was really coming back to the States from Nam. The fact that a fallen comrade who wasn't KIA in Iraq or Afghanistan can be eulogized, honored and remembered and the word spread, says a great deal about not only his unit but the whole approach the military takes towards PTSD these days.