For what its worth, here's the advice I was given by a VA therapist- my sufferer is a vet, but I think the advice may be valuable for others. The T advised that the fact pattern that I tried to be scrupulously honest in describing is a classic PTSD pattern of withdrawing and returning. Due to an existing pattern, his assessment was that it is very likely that my vet will return when he's ready. At the same time, the T advised me to consider what parameters i was willing to tolerate. In other words- decide on a reasonable- to me- length of time to wait and if he continues in isolation when that time has elapsed, i should move on.
I am aware of several stressors my sufferer is dealing with and his most recent isolation began with no warning signs for me. He works overseas, so there's much about his daily situation that i don't know about. Among other things his employment contract will end in about 7 weeks. This in itself is a significant stressor. I've made no secret of the fact that i want him to come home. He said he wants to, but is uneasy about it. I know very well that if he chooses to come home, he must do it for himself, not because it's what i want. I realize that this alone could be enough for him to need to isolate, although i have no idea if this is what caused it.
Bottom line- in my situation, there is a preexisting pattern of several shorter periods of withdrawal with him returning. He tried to end our relationship once, but didn't end communication with me. We were heading back to a greater level of intimacy at the time he most recently isolated, along with the pending end of his employment contract. I have heard from him once- he let me know he's ok and thanked me. That's it.
I have decided to heed the therapist's advice and give thought to a reasonable period of time for my sufferer to resume some sort of contact, although I am prepared to reconsider my time frame, if it seems like the right thing for me to do when the time comes. My sufferer was in therapy in the past, although his current living situation made that difficult to continue, he's also compliant with his meds. These factors will certainly make a difference.
Clearly there's no one size fits all answer. However, I do think that the advice to decide how long a supporter is willing to wait and then move on, is a sound recommendation.