Closing the distance without giving an ultimatum

Im 34, he’s 33, we’re 5 hours apart. Been together for 18 months now, a little over a year of that is long distance. We see each other once a month for a weekend, sometimes twice if it works out.

We don’t have an end date to this and I think maybe that’s the issue. Originally I was considering moving to his state around May when my lease is up but if I do that it puts off my nursing program that’s starting in January and I really can’t do that right now. I need to finish school. Recently he brought up moving back here to be closer to me and his kids. I know he loves his carefree “single” life, he loves the people he works with/friends there and the job he’s at. When I bring it up it’s just “soon” or he’s working on it and he promises he’ll move back. No details or anything actually planned which makes me feel like he says one thing but doesn’t actually mean it. I know if he changes his mind or drags it out and doesn’t actually move I’m going to be upset and it will probably be the end of this. I’m pretty much over the distance at this point. Im at a point in life where I want to be in a real relationship and go on dates and spend time together.

How do I bring up a serious conversation about this without giving or making it sound like an ultimatum?? I get that it’s his choice, I don’t want to pressure him or make it seem like a threat to break up if he doesn’t. I don’t want him to move back and then resent me because he’s not happy. But I also know I’m not happy doing LDR anymore, realistically I can’t make this work for another year and a half through nursing school.