I think it depends on certain things.
First, the break up. Was it a bad breakup, what where the reasons, was it something unforgivable or was it both of your faults?
Second, were you friends before being romantically involved? Where you close friends during your relationship? Do you guys have anything else besides the romantic and sexual connection?
I think you shouldn’t because if you want to move on, it’s impossible to do it. You will always have a connection with your ex, so its better to closed that chapter of your life.