Is the 'silent treatment' normal?

I have anxiety and ADHD, both of which I am treating.  Anxiety is the greater challenge, and in the past I have been rather hot-headed and prone to making huge issues out of tiny ones.  Lately with the help of meds, I've been able to notice that not every issue in our relationship is my fault.  My boyfriend also has an anxiety disorder, but refuses to recognize it.  His stress can be off the charts, usually resulting in 3-6 days of unendurable crankiness.  We don't live together, so I avoid him when he gets into one of these moods.

Yesterday we went to the baseball game with our friend James.   Before we got there, I lost my patience and snapped at him over what proved to be a hot-button issue for him.  I sincerely apologized and hugged him.  But instead, he shook me off, tore into me, and told me not to talk to him.  (That's pretty unusual.)  We went to our seats, but after one inning I couldn't take the tension, so I excused myself and watched the rest of the game from the gift shop.  When it was time to leave, I walked ahead alone.  We got to the car and he asked me "What was that all about?" and I explained honestly (and with no tone in my voice) that I felt extremely uncomfortable and thought he and James would have a better time if I left.  He didn't speak to me for the rest of the ride home, and when James left, I told my boyfriend, "I know you don't want me to talk to you, and so I'll honor that, but... I'm sorry."

And... Silence.  For the rest of the evening.

My boyfriend does this all the time, especially when he's stressed.  He says isolating himself from me after an argument is his way of clearing his head.  He says he needs his space.  But is the silent treatment really the same thing as needing space?  I think an hour or two of going to our separate corners and taking a breather is normal, but all night?  Depending on how big the issue was, he might isolate himself for up to a week.  He claims he is not ignoring me, and also that he isn't spending the time sulking, but there is no communication from him whatsoever.  I am glad to give him his space, but I feel that isolation from each other for more than 3-4 hours is ridiculous.  What do you all think?  Is this normal?

We've talked about this a zillion times before, and he knows this hurts me deeply. I feel so disrespected and depressed.  We've been together for over two years, and I don't deserve to be isolated for days on end.  How can this behavior work in a marriage?  Will he refuse to speak to me and sleep on the couch?  This does not seem normal, but there's nothing I can do to change it.   He refuses to see it as a problem, and says I just don't understand what "needing space" is.