Thanks!
You'll definitely want to make sure that you give the creatures enough time to show their behaviour before the selection process kicks in, otherwise the algorithm has no way of knowing which ones are the best / have the best strategies. One of the biggest mistakes I see people make is setting the time per generation to 1 sec and then wondering why nothing happens. Lowering the time per generation is not equivalent to speeding up the simulation overall.
As far as how many generations you'll want to wait I'd say that depends on the complexity of the creature and also on luck. If your creature is complex (i.e. it has a lot of muscles) then it's going to be more difficult for it to learn how to coordinate all of those compared to a creature that only has one or two muscles. However, since the initial brains are completely random you might get lucky and end up having a couple of creatures in your first generation that already have a decent strategy - in this case you'll see them progress a lot quicker - or you might get unlucky and start with a bunch of creatures that just do nothing at first. If you see them still just do nothing after about 15 generations I'd just restart the simulation and hope for a better group of starting creatures.