As we all know, Hanna-Barbera used The Honeymooners & You'll Never Get Rich (The Phil Silvers Show, aka Sgt. Bilko) as templates for two of their primetime entries in the 60's, The Flintstones & Top Cat, respectively. The failure of Top Cat brought about not an end to that formula, but a little tweaking, as the studio would use movies as templates for later series (i.e. Wacky Races, which evolved from "The Great Race").
In the 70's, they would return to the formula, using All In The Family as a touchstone for the syndicated Wait 'Til Your Father Gets Home, which lasted two years, and The Waltons for These Are The Days, which failed after 1 season. Meanwhile, rival Filmation went in a different direction, opting to "continue" some shows that had already been cancelled in animated form. It didn't always work.
The first such case was Star Trek, which finished its original 5 year mission with 21 new episodes, spread out over 2 seasons (1973-5). As such, it was the first series the studio sold to NBC, and by far its most popular. It was the 2nd collaboration between Filmation & Paramount, as the first, The Brady Kids, an animated spin-off from The Brady Bunch, was in its 2nd & final season on ABC. Unfortunately, save for brief cable runs on Sci-Fi (now SyFy) & TV Land in the 90's, the animated Trek hasn't seen the light of day in years, while the live action version has thrived in syndication seemingly forever. Try figuring that one out.
After Brady Kids was cancelled, creator-producer Sherwood Schwartz replaced it with an earlier property for ABC, resulting in The New Adventures of Gilligan, which, some might argue, would constitute Season 4 of Gilligan's Island, since the setting was the same, and the cast was retained, save for Tina Louise, who'd distanced herself from the franchise, and Dawn Wells (other commitments). Eight years later, Filmation & Schwartz would try again with Gilligan's Planet, which was just a reboot of the earlier series, and a bad one at that, as I've been told. In between, of course, the castaways had returned home, then relocated to their island, turning it into a tourist attraction in 3 TV-movies for NBC, produced between 1979-82 (And produced by Universal, which had 0 to do with the original series. Go figure.), so the original concept really wouldn't be feasible anymore. Planet would also be Schwartz's last Saturday morning entry.
By the same token, that same year (1974), H-B tried to keep The Partridge Family in play, even though the series had been cancelled by ABC. CBS picked up Partridge Family 2200 AD after rejecting Joe Barbera's pitch for a Jetsons update that would've been along the same line as Pebbles & Bamm-Bamm 3 years earlier, with Elroy & Judy now older. Since Pebbles didn't get ratings along the level of, say, stablemate Scooby-Doo, the show was cancelled, then reworked into the Flintstone Comedy Hour as a last-ditch effort to keep the teenage version of the title characters in play.
Suffice to say, without lead players David Cassidy & Shirley Jones, the futuristic Partridges bombed.
Back to Filmation. In the same year that they picked up Star Trek, the studio also acquired licenses for two other properties. Neither worked.
My Favorite Martians may have been meant to be a continuance of the original My Favorite Martian, although there was now a 2nd Martian (Lane Scheimer) joining Uncle Martin (Jonathan Harris, ex-Lost In Space, taking over for Ray Walston). Not all the affiliates picked up the show, as in those days, stations could cherry pick what shows they wanted to bump for local/syndicated programming. Over at ABC, Lassie's Rescue Rangers also got one season and no more, despite the concept of the collie forming an animal team to back up some forest rangers. Nice idea, but it may've been poor writing that doomed this show.
It seemed as though that was it, after New Adventures of Gilligan was axed by ABC, but in 1982, Ruby-Spears got in on the act. With 2 of the network's hit comedies having already spawned animated counterparts, they landed the license for Mork & Mindy in what amounted to a pseudo-prequel, sending the title characters (Robin Williams & Pam Dawber) to high school, and trying to retcon Mork as having landed on Earth while future wife Mindy was in high school. This, suffice it to say, was worse than Gilligan's Planet, which came out the same year. Both were gone at the end of the season.
Other celebrity toons were simply direct spin-offs from their "parent" shows. To wit:
*The Brady Kids (1972-4, ABC/Filmation/Paramount).
*Emergency Plus-4 (1973-5, NBC/Mark VII/Universal/Fred Calvert Productions).
*The Addams Family (1973-4, NBC; 1992-4, ABC). Hanna-Barbera produced both versions, the first more a direct spin-off from the Addamses' appearance on The New Scooby-Doo Movies over on CBS the previous year. The 2nd series came about after the 1991 movie with Raul Julia & Christopher Lloyd was a huge hit.
*Fonz & the Happy Days Gang (1980-2, ABC/Hanna-Barbera/Paramount).
*Laverne & Shirley in the Army (1981-3, ABC/Hanna-Barbera/Paramount; Fonzie (Henry Winkler) was added in season 2 without any closure to his own toon.).
*The Gary Coleman Show (1983-4, NBC/Hanna-Barbera). Spun off from the TV-movie, The Kid With the Golden Halo.
*The Completely Mental Misadventures of Ed Grimley (1989-90, NBC/Hanna-Barbera). Spun off from SCTV, which was airing on NBC at the time.
So, the average lifespan would be 1-2 years. It would be worth noting that Mr. T, which got 3 years (1983-6) on NBC wasn't a direct spin-off from The A-Team, as T was recast as a gymnastics coach whose charges also solved mysteries. Likewise, Swamp Thing, a miniseries that aired on Fox & NBC, wasn't directly connected with the live-action series on USA Network. Finally, Sabrina: The Animated Series, which aired on ABC from 1999-2001, is considered a prequel to the live-action Sabrina that was on the network at the time.
With the broadcast networks having all but abandoned animation, with news that Litton, which programs ABC's syndication-friendly, all live-action block, now adding CBS to their client list for the fall, would cablers like Nickelodeon, Disney Channel, or Cartoon Network, take a chance? Should they? I can think of a few recent series that could stand being rebooted as toons, under the right circumstances and situations. Let me know what you think.