I think I've built my immediate life in such a way that it would be VERY difficult to cut myself off entirely from people close to me for ANY amount of time without them staging a large scale intervention (and I think I would appreciate it once it was over with). So, these days I can go maybe at the MAX a few hours to a day and a half, at the most, before cycling back into communication. But I think I'm okay with that. It's something that would have freaked me out a few years ago, but now feels like a safety mechanism against me going to really dark and dangerous places in my head.
Long distance people are a bit different and harder to manage overall. They are also some of my most tempestuous relationships, and I find myself "breaking up" with them mentally for months at a time. It's hard because we've all changed so much in the past few years - them getting more religious and me getting less - and trying to figure out where those people fit in my life, and me in theirs, has been really difficult and painful.
Oh! I'll also add that there have been people I've cut off for years at a time. Two friends from childhood in particular, and I've cut them off twice for more than two years each time. They've been beyond gracious with me, and we've definitely had a LOT of trust stuff to work through, but the fact that they have just been there and willing to take me back each time has been huge for me. Super humbling. Really, really deeply meaningful.
Edit: and I don't say that to make excuses for my behavior. At all!
If someone has cut you off because of PTSD things, I don't think you should excuse their behavior in a way that puts down your own experience of it. I would hate it if someone did that for me, even if their asking me to take responsibility for my actions and the pain I've caused is its own kind of painful.
I honestly can't even imagine how hard it would be to not take it personally. But I think, PTSD or not, people SO often make choices at the end of the day because of their OWN stuff (needs, desire, baggage, etc), even when they think it is because of other people. I'm really sorry you are experiencing this (which is what I'm hearing between the lines). And I hope you will find a way to release yourself from it so that you can care for yourself as best as you can in the mean time.