How do you know if it's time to break up?

I've been having doubts about whether staying and trying to work things out is the right thing to do. Or if I should just call it quits.

We don't talk much and long distance is hard as it is. All we have is communication via phone. And I've told him how I feel. He tries for a day or two then reverts to his ways. His excuse is work but thats bs everyone makes time for people they say they care about.