I'm in the same boat. He's staying behind to finish out a job, and the plan is that he'll join me in fall 2019. We've been together 4.5 years and lived together for 2.5. On the upside, his mom works for an airline so he'll be able to fly out and visit pretty cheaply. I just don't know yet how often that will be, between my class schedule and his work schedule.
This might be silly, but one of the things I'm most nervous about with us being apart is our dog. The pup is coming with me, and I'm worried about leaving him at home all day alone while I'm in school (right now he comes to work with me, or goes to a daycare really close to our house - he's very spoiled!), and then if I have evening things to do (gym, or nights out or what have you) he's going to be alone then too. I'm sort of thinking of trying to find a roommate who also has a dog, so they can keep each other company, and I could share the burden of someone being home to let them out. But also haven't had a roommate in 2 years other than my SO so I'm kind of nervous about that, too.