I would never want to give anyone false hope but the general pattern of behaviour with PTSD shut outs is that people do often return. Obviously varying lengths of time will differ from person to person. Some people speak of having no contact for hours at at time to YEARS at a time. I think once you know him and his pattern better, you will be able to recognise and prepare for it each time. It will be an ongoing situation until consistent help is sought.
Its like staring up at a 50ft wave wanting to reach them and are treading water trapped behind it. You can't stop the inevitable, you both kinda have to hold on tight to something and ride it out until it passes and quiets again.
I hadn't seen my guy for 4 months since beginning of February. Phone/text contact was very minimal too. I saw him for the first time again 2 weeks ago and hugged him so tight for so long he had to say "go easy..." and laughed. I apologised to which he told me not to be silly. But I said it was because I didn't know when I would see him next so had to take my chance now. He is a very affectionate person and one good thing about shut outs is that it proves to both people whether or not absence really does make the heart grow fonder and if as a team, you're strong enough to make it.
The last 4 months has not been our longest time apart but it has been the toughest. I think the flood of emotions and rib cage breaking, bear hug embrace overflowed his cup all over again and he has gone away to have time to figure out what to do with them/me? I was surprised how overwhelmed and emotional I was too so he must have freaked the F out! Still, it communicates one very important thing...for which I am grateful and happy.