My fiancée moved in just before what is reputed to be my hardest semester in PT school, and it went fine. Granted, she was also working long days during that semester as well, so the routine was basically get up at 6am and see each other again around 9pm for dinner. But in general, my study habits just shifted to making sure I stayed at my building after class and put in a couple hours before going home and not studying, when I'd typically take a break before studying in the evening when I lived alone. It is nice to have someone there to pick up the slack in daily responsibilities when you have a particularly busy week/weekend of exam studying. PT school isn't a steady-state of busy throughout the whole semester, so I contribute more when I have a slower week. Our relationship does better when we are both engaged in meaningful pursuits, it makes the time we do have to spend together more meaningful and keeps us feeling productive.