When one season of an ongoing TV series finishes, how do they determine when to release that season on Blu-ray/DVD?

For a couple ongoing shows I follow, they have been releasing the Blu-ray/DVD of the last completed season just before the new seasons starts. If you missed the prior season, it's a long wait, then a rush to catch up on Blu-ray/DVD so you can jump into the new season. I am ignoring iTunes or other ways to watch the shows.

(I am thinking of Breaking Bad, Walking Dead and Game of Thrones. However, the last season of Breaking Bad came out three months before the show picks up again, although one still had to wait eight months after it had completed.)

This has been SOP for a while. Clearly it's to help promote the new season.

If you missed the previous season and plan to watch the new season, I would recommend recording the new season until you catch up.

Like Salty said, the releases are usually scheduled 2-3 weeks prior to the new season to promote the new season, and are priced high to capitalize on the people that need to catch up before the new season starts. As the newer season goes on and the older season starts to sell less, that leads to price drops and lower sale prices. That's why it's better to either stay caught up or be patient and wait.