The Peacock has gone from punchline to prizewinner in primetime.In a fall television season chock-full of change and overall declines for the Big Four, long-lagging NBC has vaulted to the early ratings lead among young adults. Granted, it’s doing this mostly with hot two-night reality show “The Voice” and NFL powerhouse “Sunday Night Football,” but the music talent show has also served as an important lead-in for the net’s highest-priority new scripted skeins. As a result, Monday’s post-apocalyptic drama “Revolution” and Tuesday’s Matthew Perry comedy “Go On” have been given a real shot at finding and keeping an audience. The NBC surge — it won the season’s first two weeks in adults 18-49 for the first time in nine years — proves that, in an era of fractured viewing and close margins in the ratings race, the difference between first and last place is just a couple of big shows. Of course, it helps that the Peacock is popping at a time of declining fortunes at its rivals. Longtime leaders CBS and Fox have both sprung more holes than expected, while ABC remains in rebuild mode. Through two weeks, NBC was up by about 15% vs. last year, while the other major nets were down by double-digits. Every network, meanwhile, is dealing with diminishing ratings returns for most shows — at least in the next morning’s ratings. National DVR penetration has risen to 46% (from 42% last fall), but the rate among adults 18-49 is now 51%, meaning that more than half of the audience that the networks primarily target can watch their favorite shows on their own timetable. While breakout hits and insta-bombs are still apparent in just about any ratings data, an exec at one net referred to this season as “a tipping point” in the way that audiences consume shows, and that for any program that exhibits even some level of ratings spark, patience is being preached company-wide. Or, to use the title of a new NBC comedy, waiting for DVR data to assess a show’s true performance is the new normal. This page contains some early truths from the opening weeks of the fall TV season. HITS AND MISSES NBC’s “Revolution,” which started a week before the season officially began, has looked pretty good through four airings despite continuing to fall off from its big premiere. CBS also has seen its Sherlock Holmes drama “Elementary” hold up well enough in its second episode to suggest it will be around a while. Other shows doing OK relative to lead-in and timeslot expectations include CBS’ period drama “Vegas,” NBC comedies “Go On” and “The New Normal” and ABC’s “Last Resort.” On the other hand, CBS has already shelved “Made in Jersey” after just two airings. And a pair of Monday shows, CBS comedy “Partners” and Fox drama “The Mob Doctor,” may not make it through the November sweep. NBC’s “Animal Practice” is off to a slow start as well. FIRST-SEASON MULLIGANS Fox has already renewed a pair of comedies, “Ben & Kate” and “The Mindy Project,” whose early ratings would have meant sure cancellation just a year or two ago. But the net has committed to its four-comedy Tuesday template and is hoping that positive word of mouth can translate into more viewers setting DVR season passes for these newbies. There’s also a school of thought that, especially with young-skewing shows, first-season ratings aren’t everything. If a show does decently ratings wise, is on track creatively and generating a lot of buzz, it can recruit new viewers with binge viewing via Hulu or Netflix. REALITY REMORSE In recent years, no genre has made a bigger impact on the ratings race and a network’s bottom line than reality. But because these shows often take up two or three hours a week, they can quickly turn from an asset to a liability when they lose steam. NBC ran “The Biggest Loser” into the ground a couple of years ago, and last season saw every veteran two-hour reality contest — including Fox’s “American Idol” — lose significant ratings ground. ABC’s “Dancing With the Stars” is off to another sputtering start this fall, and the Alphabet must already be considering life without it. On the other hand, “The Voice” and “The X Factor” are young enough in their runs to still hold real value. At least for now. SPORTS A GAME-CHANGER One of the biggest contributors to the trend of delayed viewing is live programming, especially sports, which is watched more immediately than other shows. This fall has seen NBC’s “Sunday Night Football” remain the primetime ratings leader, with more than 20 million viewers, while ESPN’s “Monday Night Football” is up about 10% to better than 15 million viewers. The NFL Network has started its “Thursday Night Football” package (which draws about 7 million) a couple of months earlier than usual. Add to this the fact that the later-than-usual start to the TV season means its first couple of weeks went head to head with late-season and post-season baseball games, and many viewers, especially men, are having shows stack up on their DVRs. NOT HANGING AT 10 Among all primetime programming, those airing at 10 p.m. are having the most difficult time in the DVR era. Viewing levels typically peak in the 9:30 half-hour, and consistently drop from there. And even if viewers start a 10 p.m. drama live, they often wait until the next day or later to finish it. This makes it especially hard to gauge the performance of rookie series in the hour, and why shows like ABC’s “666 Park Avenue” may get a longer leash than in past years. CABLE TAKES AIM Cable networks, which have traditionally ceded the first few weeks of the fall season to the broadcasters, have instead been more aggressive than ever. The ratings gap between most top cable shows and top broadcast shows remains large, but early in the season, there have been more examples of cable besting the Big Four in the 18-49 demo than ever before. FX’s “Sons of Anarchy” has emerged the leader in its 10 p.m. Tuesday hour — beating original dramas on ABC, CBS and NBC for the first time — while MTV’s “Jersey Shore” is running tight with CBS’ “Elementary” on Thursday. And on the second Sunday of the season, Lifetime’s remake of “Steel Magnolias” beat out the drama blocks on both ABC and CBS. And then there’s the biggest of them all, zombie drama “The Walking Dead,” which AMC unleashed this week, and was expected to again gobble up just about anything in its way.