system
Given the following post, respond as if you're commenting on Reddit:
human
[Mass Effect] What would happen to a species which had just barely avoided being harvested by the Reapers?

For example, a species that is just breaking the atom as the Reapers finish their harvest. After a few centuries, when they find the Mass Relays and the Citadel, wouldn't they have 50000 years to develop their civilization before the Reapers return? 

That might make them too powerful to harvest.

 Even the advanced races like the Asari were only space civilizations for a few thousand years old before the last harvest.
gpt
If they got too advanced too soon, the Reapers would likely turn around and head back for a smaller "reaping". The 50,000 year thing is more of a guideline of how long it usually takes for galactic civilization to pop up and get to the desired level. 

It's one of the reasons they always leave a Reaper behind as a scout; to report back when it's time to begin the harvest, even if more/less than the usual time has passed.