I've been a season ticket holder for 46 years now but whenever I wanted to add any seats or change areas (to get away from obnoxious fans), it was nearly impossible to find areas to keep all of my seats together because of how many were being held even if I had a higher priority.
Also, after you would select your seats, you were locked out and couldn't change them if better seats became available later if someone didn't renew. It was just a crapshoot at the time you selected.