If they're coming from different locations, then any one ship's path would be disrupted by "foreign" sources, making it somewhat unreliable. Worst would be when

If they're coming from different locations, then any one ship's path would be disrupted by "foreign" sources, making it somewhat unreliable. Worst would be when two sources are blowing (puffing?) at a ship between them. Or, maybe they are intended to push ships: alien ships, to keep them away. Or, maybe the ships are messages in bottles, and the senders don't care where they end up. Their current Voyagers? Our future Voyagers?