Once I have done the baseball stuff and I'm ready to start back to a pile I stretch them out to about 100 yards on the first day. Start short, identify the pile, back up send them again, backup etc. in a mowed field with visable bumpers you should have no real problems getting them to do this. If so, shorten it up, keep a bumper in the back pocket to throw and help with confusion. I don't introduce force at all until they demonstrate they remember where the pile is and then its force enroute. I don't force from my side until much later.
/Paul