Why do you think 100 light years is the edge of "reasonable travel distance"? I put to you that you are imposing your human standards on other species, assuming that what seems to you to be a long time would also be a long time to another species.

Maybe the aliens have an average livespan of 200k Earth-years. Maybe much more. Maybe they experience time differently, and for them a 100 year journey feels to them like a walk around the block.