There are no "perfect" genes. That simply defies the logic of having a genetic algorithm in the first place. If it's all towards reaching perfection, then all we need is an optimizing algorithm.

My point is, genetic algorithm interacts with a constantly changing environment to maximize the species survivability. And when the environment changes, so must the set of "good" genes as they are no longer as "good".

From the algorithm point of view, it's always better to keep as rich a gene pool as it can manage, and to create as many offspring variations as possible in order to maximize the species survivability.