User blog comment:Mike Gilbert/Do you think the Reapers should keep their powers after Synthesis?/@comment-8419211-20130518030659/@comment-26516989-20130518183724

Expanding outside the galaxy seems unrealistic. The relays allow them to travel instantly between star systems because FTL travel would take years. The distance between galaxies is far greater than that of star systems. And there is no evidence to suggest that the Reapers built relays in other galaxies.