I don't write fantasy; I write historical novels about an imaginary place.
One of the key issues will be personal honour vs. the good of the many, and unforeseen consequences.
All the Midkemia stories are part of a 'history of an imaginary place,' so I've always known the cycle covered five rift wars. I just got to the end after 30 books. So there was no particular inspiration, save it was time to finish the whole shebang.
Jigsaw Lady is the working title of a science fiction novel I've had in my head for darn near 15 years. I think I'll start work on it next year (in all my spare time) but I'd like to get it finished some day.
I don't like fantasy where a king snaps his fingers and suddenly a whole army appears and goes off to war - he's got to feed them, he's got to pay them, he's got to take care of the camp followers and the gamblers and the people who cause disorder.
There were two things going on: 1) I had already established in my own mind where I wanted to go with the next series, and having James around as a Grey Eminence would have complicated matters. He had had an amazing life and it was time to bid him good-bye.