How have DVDs changed the lifespan of TV shows?

Image Gallery: TV Shows These days, it's easy to watch your favorite TV shows on DVD. But how does this effect how long those shows last? See pictures of famous TV shows.

TV shows rely on advertising to stay on the air and in production. Even subscriber pay-cable channels like HBO and Showtime will cancel a show before its time, if the cost of production outweighs both subscriber buzz and the show's awards and acclaim. While word-of-mouth has always been somewhat important to the lifespan of our favorite shows, this doesn't always affect the bottom line.

However, thanks to the popularity of TV on DVD, this model is slowly changing. Now, the bottom line isn't just about advertising revenue and ratings, but about the entire life cycle of the show. From the first airing, to time-shifted recording, to reruns, to the DVD release, each step makes money, and each step feeds the next.

Most shows release a season of a show on DVD each year to coincide with the debut of the show's next season. This means that advertising for the current season also brings visibility to the just-released DVD of last season, and vice versa. Most shows integrate the marketing of these two separate projects -- one depending on store sales and one depending on ratings and ad revenue -- to increase the power of both.

A show or film, even if originally considered a failure in Hollywood, can be considered a success when its overseas and syndicated revenue make up the difference. We can now add DVD sales and popularity to that consideration. If a show in danger of cancellation can demonstrate its bottom line through DVD sales, it's in a much better position than it would be based simply on fan support.

And when the show finally does end, its life cycle is still not complete. As long as DVDs of the show are available, people will share them, purchase them for one another and continue to discuss the show. That means continuing visibility for actors, directors, producers and writers. Next up, we'll take a look at what this means for the future of the industry.