same argument

Pre warning this is a rant. So over the last six months me and my boyfriend of three years (he's 21/I'm 19) have had this little argument every now and then about his job, and it's slowly becoming a bigger issue. I am at uni currently studying journalism and he is a technician at a bowling alley, he's been offered a job at aldi and that would mean more money but I feel like this job will become a dead end, it won't be mentally stimulating or challenging for him. He's spoken about joint the RAF/navy every since we became a couple but more so last year and less so this year so I feel like it's not something he wants, however he constantly says he doesn't know. Even though I am young, I will be graduating in two years and I want to kick-start my career and soon followed by marriage and family. It maybe premature to think of that right now, but I do t want to waste my time on someone who in the end will be satisfied in a store when he has so much potentential. He is my first love and I don't want to leave him if he will be ready to start a career soon but I don't want to keep waiting for him to give up his adolescence and think seriously. Sorry for the rant but I needed to get my thoughts out there, and if anyone has ever been in a similar situation please feel free to comment x