It's pretty self explanatory, how do you handle evolution? I noticed the games have a pretty consistent time of evolution, for example, most people's starters in Fire Red and Leaf Green evolve around the Pewter City-Route 4-Mt. Moon area. In the anime, however, there is a wide variety of time between evolution, with some Pokemon, like Ash's Caterpie, barely spending one episode as a Caterpie before evolving, while others, such as Ash's Pidgeotto, spent 78 episodes before evolving. So, how does everyone handle evolution in their writing? Is it closer to a game approach, where there's a measure, formulaic approach? Or is it more of an anime, and most other media, approach, where they evolve when it serves the purpose of your story?
As an add on: How early is too early? (In terms after chapters, as a rule of thumb, barring specific instances.) And how long is too long? (Again, barring specific instances.)
I'm just curious because I'm trying to figure out when my main character's starter should evolve, round about, and was wondering what approaches other people have taken.