Re: Logen Ninefingers and the rest (spoiler alert)
I thought that the major story arc of the First Law trilogy, which was about the First Law, came to a satisfactory - if not completely happy - ending. That the characters' stories may carry on (if only in the readers' imaginations) is fine as far as I'm concerned.
This sort of ending is far preferable to those where the characters' stories reach their conclusions, but the plot peters out rather than being concluded.
For myself, I wouldn't mind meeting the major characters again; nor would I mind seeing another book (or trilogy) about how the struggle between the Magi carries on after the events of the First Law trilogy.