Bf wants to join the Air Force? What should I do?

My boyfriend's dad was in the army, and my guy commented recently on how he may join the Air Force when he gets out of college. He has all these dreams of being in the military even though he's asthmatic and blind in one eye. Although I've heard that Airmen have a less dangerous life than guys in the army, I still don't want to be with a military guy, especially if we have to move all the time or he gets sent overseas. At the time, I wanted to say, "You can do it without me." But I didn't because I didn't know if it would be wise to issue an ultimatum if he didn't even know he wanted to do it. Should I say anything about it the next time he brings it up, or broach the subject myself? I don't want to wait for him to graduate and be with me, only to have him decide he's going to join the Air Force and go God knows where. Am I wrong to feel this way? Should I worry at all? How do I deal with this?