No, when they run away.
The thing is, is that they can attempt escape through you again, and it makes no sense for them to perpetually be running away farther and father away from the system.
The problem with the way the fleets are now, is that the player generally needs to prey on smaller or similar-sized fleets, which tend to be faster, but only by a couple points. This results to things like the player camping the spawn points, and other exploitive tactics
The idea here is that:
If the fleet is really fast, it won't turn around and attempt to initiate an [escape] battle. Makes sense, since they can both easily outrun you to safety, and they know they stand utterly no chance.
If the fleet is marginally faster, they might turn around after a while, and then attempt to [escape]. They realize that they aren't getting anywhere useful fast, and they do stand a chance of survival
If the fleet is of equal speed or marginally slower, they will turn around pretty quickly, and try to [defend] or [escape]. They stand a chance at survival.
If the fleet is significantly slower, well, they don't fall within the scope of this issue.