What I find upsetting as well is when they are with you in body but not in mind as it were. There would be times when he was back from patrol, and all he could think about was the damn submarine. They tend to forget that we still exist and get on with our lives when they're away. I used to point out that I didn't go into a state of suspended animation as the boat passed Devil's Point and disappeared into Plymouth Sound.
He came back from patrol once, when I was 6 months pg with DS, was in the house for 2 days, and then buggered off for a sailing holiday with a friend. He was then due to go back to sea for various things from mid Sep-Nov, and I knew he probably wasn't going to be there when I was due to pop, so I wasn't very happy. Sadly, the yacht developed engine trouble, and they had to come back after three days!
It wasn't too bad when he was at sea, or weekending when he was at the Staff College, but I have to say that when he moved to Brussels to work, it was a killer as we only saw each other every six weeks. There was just this feeling, even though we talked every day and e-mailed lots, that it could all slip away. You lose each other because your lives don't overlap much, hence the move to Brussels for DS and I. Even so, he is still away regularly for meetings, though it's not as bad as it used to be.