So many TV shows went missing this winter, viewers were ready to call out bloodhounds.

After airing just four episodes, "V" disappeared from ABC and didn't return until last week. The Fox hit "Glee" went on an extended semester break that will stretch until April 13. ABC's "FlashForward" (7 p.m. Thursdays) and Fox's "Fringe" (8 p.m. Thursdays) both left mysteries hanging during lengthy hiatuses.

An unusual number of shows took long breaks this season, leaving some fans puzzled and worried. But breaks of three or four months no longer mean a series has been canceled. They're just more evidence of the broadcast networks' continuing search for new ways to program the TV season.

We can blame ourselves for making the change necessary. After happily watching reruns since the dawn of television, viewers stopped being so eager to see the same episode twice. In the 1990s, an explosion of original programming on cable gave us plenty of fresh choices, and recording devices kept us from missing our favorite programs the first time around.

The networks tried slipping repeats into the broadcast season, but with more and more shows featuring serialized elements, random reruns proved confusing to audiences. So did scheduling frequent weeks off, as ABC tried disastrously in the first season of "Lost."

Meanwhile, cable networks were getting lots of attention airing short seasons of original series and making fans wait months for new episodes. On HBO, "The Sopranos" ended its first season on April 4, 1999, and didn't return until the next Jan. 16. The audience came back, too.

Broadcasters began talking about year-round scheduling and looking at cable (or British) ways of doing business. Fox led the way, succeeding when it delayed the Season 4 premiere of "24" to January 2005, allowing the day to unfold without interruption. With baseball in the fall, Fox tried a different strategy with "Prison Break," starting the serialized show in late summer 2005 and then picking it up again after several months.

NBC has since experimented with airing "Heroes" in so-called chapters, each making up part of a season. And "Chuck" (7 p.m. Mondays), renewed last May, was held back to January so its episodes could run in sequence.

But this year's hiatuses, while they might be seen as a test for how network TV might look in the future, actually were more happenstance than strategy.

The "Glee" break was scheduled, in part, because creator Ryan Murphy was committed to directing a movie ("Eat, Pray, Love," starring Julia Roberts). Fox also got a chance to whip up interest in the musical-dramedy, releasing the first half of the season on DVD and announcing a concert tour for the cast.

FLASHING FORWARD

ABC had always intended to run "V" in chapters, ABC Entertainment president Steve McPherson explained.

"We did not intend for the first chapter to be so short," he said. "There were production issues that took over, unfortunately." (In other words, the show was going wrong, and producers and writers sat down to regroup.)

As a result, the network decided on "a kind of limited chapter" of four episodes to run in the fall, with a consecutive run after the aliens-on-Earth drama's return.

"FlashForward" was already on the air when ABC noticed that "repeats really weren't working," McPherson said. Since the Olympics were set to air on NBC in February, the network decided to hold "FlashForward" back to March and promote it alongside "V" as an event.

"It wasn't something that we intended, but we dealt with the circumstances, I think, in the most productive way we could," he said.

Executive producer David S. Goyer defended the "FlashForward" hiatus as the only thing that made sense, telling TV critics visiting the set in January that all involved had decided that airing the remaining episodes consecutively was the best course. However, Goyer has since left the show, and "FlashForward," whose viewership had declined (down more than 40 percent from its premiere) even before the hiatus, returned last week to unimpressive ratings.

But as long as viewers ignore reruns, the networks will be forced to look for new ways to fill the TV year. Why not just dispense with repeats altogether and make enough episodes of a series to fill a whole year, or at least a nine-month season? Because that's far too expensive; networks need to air an episode at least twice to get their investment back. Cable networks air shorter seasons anyway — typically 13 episodes, compared with 22 or 24 for a broadcast network — and run each episode multiple times, making their business model inherently more profitable.

CBS, which still airs its shows on a traditional September-May schedule, does well with reruns, largely because the procedural dramas for which the network is known perform well in repeats. More ambitious, often serialized shows might not repeat well, but they draw younger audiences and do well on DVR playback.

"FlashForward" could be a test case for whether a new show can survive the hiatus strategy. If the series, which ABC had hoped might be a long-running replacement for "Lost," ultimately fails, ABC might be more inclined in the future to run shows like "Castle," a nonserialized, character-driven drama that McPherson calls "our highest-performing repeat show."

Then no hiatus would be necessary.