That is called cooking. It is definitely an intelligent process.
A GA is terminated (it doesn't end on its own) when the programmer/researcher decides he has an answer he can work with.
And how does he decide that? Flip a coin?
Imagine I give you a 30 element network to create a 20th order bandpass filter. You have unlimited choices of resistors, capacitors, and inductors to use. I want that filter to have a Chebychev response with a defined passband gain, passband ripple, and attenuation outside the passband. ...
...
But your problem is to figure out how to make one that YOU believe is pretty darn good.
Type I or type II?
You start here.
P.S. A bandpass filter is a filter that "attenuates" outside the passband.
P.P.S. There's a heck of a lot more information needed than what you provided. Power supplies, loads, temperature conditions, stability over time and or temp... etc.