Hold the farewell parties for "Heroes."

The NBC drama looked as if it were about to fade into oblivion based on the same-day ratings for its first couple of episodes this fall. But when results from the playback of the show over a seven-day period on digital video recorders were released Monday, the picture for "Heroes," as well as almost half of the shows on network television, brightened considerably.

The overall audience for "Heroes" grew by 26 percent from the numbers that were reported the day after its premiere episode was shown two weeks ago; more significant, among the viewers NBC most cares about, ages 18 to 49, "Heroes" jumped from a 2.8 rating to a 3.7, well above the average for network programs.

Across network television, shows during premiere week got a substantial lift. For about half the shows in prime time, 51 in all, ratings for ages 18 to 49 grew by more than 20 percent when the seven-day DVR playback results were factored in.

"This confirms what we've known: the DVR is our frenemy," said Alan Wurtzel, the president of research for NBC, meaning the recording devices are both friend and enemy to network television. That's because the devices clearly offer the opportunity to expand the reach of network shows but they also allow viewers the chance to skip through commercials, a serious concern for advertisers.

But David F. Poltrack, the chief research officer for CBS, argued that, without reservation, "the DVR is a good thing for network television." He said, "One thing that has most limited viewing was shows being on against one another. The DVR has made it easy to watch any show you want."

Over all, Mr. Poltrack said, the numbers released Monday mean that advertisers are getting more bang for their buck. "It is showing that the relative value of our product is getting better," he said.

Under the system accepted by networks and advertisers in 2007, program ratings are no longer the currency of the medium. Advertisers now pay based on the ratings for the commercials, measured both on the live airing of the show and whatever playback takes place over three days.

The ratings released Monday include playback over seven days. As Mr. Poltrack pointed out, any viewing of commercials taking place after three days is being delivered to advertisers free. Conventional wisdom is that viewers who record programs skip though all or most of the commercials. But Mr. Poltrack said that CBS research indicated about 44 percent of commercials were still viewed during playback.

Apparently DVR usage has increased significantly this season. Last year the growth in ratings from live viewing to live plus seven days was 19 percent for premiere week; this year it was 28 percent.

For some shows, that may be the difference between being labeled a potential hit and a true hit; for others it may be the difference between continuation and cancellation.

One new entry, the ABC drama "Flash Forward," looked even more to be a real hit because its rating increased to a 4.9 from a 4.0 in the 18-49 age category. CBS's move of "The Mentalist" to Thursday at 10, which seemed a bit disappointing in its first week, was more positive when playback was factored in. Its rating bounced up to a 4.6 from a 3.6.

Shows with special appeal to young viewers - "Heroes" was in that group - had the biggest percentage increases, validating the view that young viewers were routinely recording shows and watching them later. The CW network, with a core audience of young women and girls, had the biggest increases of any network, including the show with the most time-shifted viewing.

The CW drama "90210" increased its rating by 35 percent when the seven-day recording period was taken into account; and the overall percentage of its audience that watched the show recorded was 48 percent.

Close behind was the NBC comedy "The Office," which also has a sizable audience of young adults. On Thursday nights, that series faces powerhouse shows on the other networks, including "Grey's Anatomy" and "C.S.I." With DVR playback, ratings for "The Office" jumped to 4.9 from 3.9, with 44 percent of its viewers watching a recorded version.

"Grey's," meanwhile, added more viewers than any other show, three million, making it the most recorded show on television.

The results for commercial viewing after three days are being released Tuesday; they will determine the actual moneymaking strength of the shows.

Mr. Poltrack compared the live-plus-seven-day results to the way networks sell their sports programs. "We all know there is a lot of out-of-home viewing for sports events, and there is a premium value that is included in the way we sell those programs," he said.