Leno moves to prime time, blocking out the 10 p.m. slot Monday through Friday. He gets breathless stories all week. (The Times has been covering it almost daily.) As with so much writing on the doings of the networks, it’s hard to rectify the coverage with the actual viewership of the show.

Leno gets roughly 4.5 million viewers a night, or 1.5 percent of the population, roughly. Two million of them, or a lot less than half, are younger than 55.  People older than 55 a) are not particularly sought after by advertisers and b) don’t much like change when it comes to TV watching.

Here’s what I don’t understand about the move. You had to give NBC credit for gritting its teeth and bumping Leno out of his slot and bringing Conan O’Brien in; I think O’Brien isn’t very funny and will suffer against Letterman, but he’s a brand and part of the network’s long-term plan, and Letterman’s not going to be there forever. The trouble with most TV networks is calcification, not revolution, so there’s nothing wrong with taking the PR hit as you proceed with some creative destruction.

But what are the costs of giving Leno a prime time show? The network’s position seems to be that 10 p.m. weeknights were a loss in any case, so why not position Leno there for a few years so he couldn’t run to ABC? (Beyond that, the costs of Leno’s show are minuscule by prime time standards.)

That’s the line the papers are taking in their coverage. The trouble is that this is a triage move, not a programming one. Won’t dropping down the oldest-skewing of all the late night shows into prime time age that audience further?

Indeed, the Week in Review (!) story today on the move comes from the point of view of a self-described baby boomer who says he’s glad the show’s going to be on earlier … because he’s been having trouble staying up to watch Jay of late. The story reminds us that “baby boomer” is now synonymous with what used to be called “senior citizens”:

Anyone of a certain age who has struggled lately to watch late-night TV knows that to succeed you have to get through the midnight dead zone, when there’s often a six-minute commercial break that feels like eternity. You yawn, you stretch, you weigh the channel clicker in your hand, you decide to “rest your eyes” just for a moment. And then, hours later, you wake yourself with a snort, wondering where on earth you are. It’s like coming back from the dead.

Now that’s entertainment!

And hasn’t that guy heard of Tivo? The Times story on Saturday stressed the supposed unique nature of the show’s blanket position, but in recent years we’ve seen both ABC and Fox do something close to that as they held onto the tail of a dragon of a game-changing franchise. In the end “Who Wants to Be a Millionaire” became an almost crack-like problem for ABC, of course, but Fox seems to have learned from that and has “American Idol” under control. (It may never be a gargantuan ratings-getter again, but it’s not going to tank Fox if it disappears tomorrow and it made the network enormous amounts of money. And talk about cheap!)

Leno’s viewership will rise in the earlier slot, but it’s hard to imagine him becoming a franchise like either of those; in the meantime, he’s going to knock the network’s average age up, and it’s hard to imagine the teen blockbuster movie of the moment clamoring to get ads before his audience.

And isn’t it portentous that NBC is relieved it can dispense with a third of its weekday programing chores by means of a show with so little upside? I mean, why not run four hours of Today in the a.m., and three of Jay at night? (It would certainly solve the network’s Ben Silverman problem.) In the end, the move may come to be seen as a watershed, where the networks’ retreat became plain.