I can understand what you are saying fjtorres. There are some book series that seem to out live their welcome or over develop their characters.
Honor Harrington seems to be a good example of this aspect. The series started when Honor Harringtion was a Captain and proceeded through several novels in which author David Weber advanced her to the rank of Admiral and made her pals with the queen of Manticore. Not much else to take her, besides she was run out of the Manticore naval service once already in the series, except perhaps to make her Chief of Naval Operations. I have not read the latest book in the series as yet, I intend to, however David Weber seems to have transferred the spotlight to one of Honor's pals, don't recall her name.
However there are some series where the characters never seem to be worn out such as the Mack Bolan saga and the component series. That saga seems to be in the 600 novels or so and still going and after reading as many of the books as I have I feel like if Mack walked in the door of my home I would recognize the man.