What happen if for example, I wait before any attak to reach the maxiumu number of ships I can afford? The resource are illimited so actually is a viable option...
It all somewhat depends on some settings and for the rest it all depends on the situation.
Lower difficulties means time has little to no meaning.
The setting to periodicly increase the AIP is ofcourse a very direct influence.
When you just became neighbour to a planet and want to conquer it as well you are often better of taking it
asap after putting it on alert.
Also delaying an attack on a planet may actually mean it becomes more difficult to take later on when your AIP is higher.
Sometimes you cant afford to become much weaker, other times time is against you ...