It is GOOD that he is communicating this with you so I wouldn't be scared of it. He isn't warning you, he is acknowledging that like everyone in recovery there are going to be times when his sobriety is challenged, hence he needs to go to more meetings or do whatever it takes so that those feelings (or cravings) pass.
You won't be able to predict it so I wouldn't put it in your head at all. It is something he has to be aware of, thats all. My RABF relapsed after a healthy stint sober and looking back there were things I now know were indicators but unlike your boyfriend, he didn't reinforce his craving with going to more meetings, he started going to less meetings due to work. Bad bad thing for someone early on in recovery.
Some go into recovery never to use/drink again but others relapse a few times before 'getting it'.