Atra du evarinya ono varda.
Doesn't take that long for me. I usually have my team planned out ahead of time, and even if I haven't already, I have this list of Pokemon in mind sorted into typings that get considered into my team if I come across them. Once I make my team, it is more or less final. The only exception is when I find another Pokemon that has better battle potential than one of the ones I already have in my team, for example Ampharos -> Eelektross in B/W2. If a Pokemon I'm searching for is not available earlier on in the game, I will save a spot for it until I finally encounter it.