More than they grow from time to time, I would prefer them to have grown emotionally from the start...
I wont even bother to read it if the main char isn't well developed from the start. I think that's how it should be. If they have time to grow, grow in Power or maybe even looks would be better 😀

I think it's not so much an issue of whether they need to "grow more" by themselves. Rather, character development should occur naturally, and it becomes really unnatural when the character Doesn't change even though:

• He grows up. Why are you still acting like a 10-years-old when you're grown up?
• All the circumstances around him changes. Any normal person has slightly changed views of the world after experiencing more of the world.

If the character is already an adult who has a defined personality and has seen a lot of the world, then yeah, there's no reason he has to change.