Hmm, well, as for surviving the defence--I varied between offering freshly-baked cookies (I, ahem, go into baking mode when there is stress around me) and offering to yell at his supervisors for overworking him. I think it helped relieve his stress that I was stalking around the house (with cookies) all annoyed at his examiners. He ate the cookies; he didn't really need me to yell.
It helped that I am genuinely fascinated by what he's working on (Physics) so we could talk about his thesis and work out some things together but, yeah, I mostly kept my head down and proffered chocolate chip cookies.
The conferences! I think marriage (or funeral) is basically the only way out! At one point, my husband flew in from Spain, was home for two days, and then flew out to Poland. It seems to have calmed down a bit, at least through the holidays I hope. I *miss* him when he's gone--although I do tend to go to the gym and scrub the house down for lack of anything else to do--so at least it's clean and I'm sort of in shape!
Seriously, I have had, a few time, to remind him that he's not living by himself anymore, and that I would like to see him more than ten minutes at a time really late at night. He's gotten better (we now set aside Saturdays to hang out ALL day together and don't run errands or anything), but he did get used to a really hectic schedule while he was living alone, and he has had to adjust it a bit. I think they can work the PostDocs and PhD students unbelievably hard, so having someone in their corner reminding them to go outside and take a walk is a good thing.