To avoid beeing stuck in a local maxima, its good to have random
Jumps in the Mutation rate and selection strenght (How many of the top % survive)

Like 100 generations with a low mutation rate and hight selection competitiveness, and then 10 generations
with a very high mutation rate and less competative selection.
Kind of like introducing ecological shocks.

So the "convenient" periods are used to optimize to a situation,
and the agressive and stressful time offer a potential
for novel combinations to jump out of the local maxima,
that would otherwise loose against the
population residing in the local maxima.

(eg, mammals evolving when dinos got kicked in the but)