It has been said of TV shows and TV personalities: "The longer you're on, the longer you're on." The fall season brings a host of new and newish series that come and go rather quickly. But those that stick around tend to endure. And in the cable reality business, longevity can approach infinity.

Which brings us around to the 15th season premiere of "Project Runway" (8 p.m., Lifetime, TV-PG).

I was impressed with this series when it began. Tim Gunn brought an avuncular, professorial vibe. He could say more, and teach more, with a raised eyebrow than a million profane tantrums from Gordon Ramsay. I knew nothing, and cared less, about fashion, but found the creativity of the contestants compelling. Entertaining. Inspiring, even.

But at the end of the day this is a reality competition, with all of the repetitive, fake and formulaic elements that the genre requires. I don't think I've watched an entire episode since the season when Christian Siriano won. That was the fourth season. Have I missed anything? Has anything changed? Should I care?

For those who do, the first episode of "Runway" introduces the new batch of contestants. The sewing and stitching follow (9 p.m., TV-PG).

Unlike many reality series, say, "America's Next Top Model," the graduates of "Runway" have gone on to have actual careers. Siriano designed the dress that first lady Michelle Obama wore to the Democratic National Convention in July.

One of the secrets to the success and longevity of series like "Runway" is their repeatability and availability to viewers. Like controlled substances, some cable series are habit forming. "Runway" wasn't terribly popular when it debuted on Bravo. But when the network devoted whole weekends to "Runway" repeats, viewers got hooked.

Networks have a harder time getting viewers' attention. It's particularly difficult when sports schedules upend audience habits. CBS' regular Thursday night comedies have given way to NFL "Thursday Night Football" (8 p.m.). But CBS only has rights to the first half of the football season. Comedy returns on Oct. 27, when football fans will have to migrate to the NFL Network for their football fix. Got that?

- Speaking of broken habits, "Beauty and the Beast" (9 p.m., CW, TV-14) airs its series finale tonight. This fantasy never caught fire. It didn't help that the CW kept "Beauty" on the shelf for seasons at a time, airing it sporadically, often in summer.

- The History Channel's multipart update of "Roots" can be streamed on Hulu, beginning today.

Tonight's other highlights

- "Craft in America" (8 p.m., PBS, TV-PG, check local listings) enters its eighth season.

- Documentary filmmakers follow the Jeffersonian gang on "Bones" (9 p.m., Fox, r, TV-14).

- Rhodes cares for Downey on "Chicago Med" (10 p.m., NBC, r, TV-14).

- Pressure gets to Annalise on "How to Get Away With Murder" (10 p.m., ABC, r, TV-14).

- Teresa struggles to escape and help Guero on the season finale of "Queen of the South" (10 p.m., USA, TV-14).

- Sam deals with several issues unique to females on "Better Things" (10 p.m., FX, TV-MA).

Cult choice

An aide (Kirk Douglas) discovers a general's (Burt Lancaster) plot to stage a military coup in the 1964 thriller "Seven Days in May" (9:30 p.m., TCM). Directed by John Frankenheimer, featuring a screenplay by Rod Serling.

Series notes

Griffin Grey attacks Harry on "The Flash" (8 p.m., CW, r, TV-PG) ... On four episodes of "Superstore" (NBC, r, TV-14): a wedding sale (8 p.m.), an all-nighter (8:30 p.m.), dating and status (9 p.m.), the "u" word (9:30 p.m.) ... An ex-girlfriend needs help on "Rosewood" (8 p.m., Fox, r, TV-14) ... On two helpings of "Grey's Anatomy" (ABC, r, TV-14): Owen and Amelia cross an intimate threshold (8 p.m.), Amelia needs help (9 p.m.).

Late night

Danny McBride and Colvin & Earle appear on "Conan" (11 p.m., TBS) ... Tracee Ellis Ross, Andrew Rannells and Phantogram are booked on "The Late Show With Stephen Colbert" (11:35 p.m., CBS) ... Jimmy Fallon welcomes Norm Macdonald and Kiiara on "The Tonight Show" (11:35 p.m., NBC) ... Eddie Murphy, Gaten Matarazzo and Schoolboy Q featuring E-40 appear on "Jimmy Kimmel Live" (11:35 p.m., ABC, r).

Sen. Bernie Sanders (D-Vt.), Billie Lourd and Young the Giant visit "Late Night With Seth Meyers" (12:35 a.m., NBC) ... Jimmy Kimmel, Patrick Dempsey, Renee Zellweger and CL appear on "The Late Late Show With James Corden" (12:35 a.m., CBS).

kevin.tvguy@gmail.com