Most Helpful Guy
Usually, it happens within 3-8 months for me. It's happened 3 times. Never once did it work out in the long term though.
In my opinion, don't wait. Live your life and see where it takes you. If at some point he comes back, then talk to him, see where it may go if you still want him, but don't sit around on the hope that he may want you back some day. That's just unhealthy.
It also depends on how you broke up. Was it mutual or was it a bad breakup where one person hates the other. If there's still love there, there's a chance he may come back but it's very hard to give an opinion without all the details.
Most Helpful Girl
Think about why you want him back first, and if having him back will better yourself and or make an improvement in your life. Don't want him back just because you miss him, sometimes we can miss things but better off not to have them. Anyway, my ex came back probably after 3-4 months.. however I felt myself wanting something that no longer existed, the relationship was completely different.