Los Angeles ? All good things must end, except in Hollywood, where pretty much anything that finds an audience the first time becomes ripe for a follow-up.

Studios this year are delivering a record 25 sequels or prequels, the big onslaught starting with pre-summer releases of “X2: X-Men United” and “The Matrix Reloaded.”

Sequels used to be hasty carbon copies meant to wring out a few more dollars from an earlier success. Studios today have learned that putting more thought and resources into follow-ups can produce franchises with bigger returns.

Hollywood’s never-ending stories this year range from highly anticipated installments in “The Terminator,” “Tomb Raider,” “Charlie’s Angels” and “Legally Blonde” franchises to lower-profile horror and animated movies like “Jeepers Creepers 2” and “Rugrats Go Wild.”

Most weekends during the busy summer season bring at least one sequel or prequel, while fall and early winter are packed with such encores as “The Lord of the Rings: The Return of the King,” “The Matrix Revolutions,” “Barbershop 2” and “Scary Movie 3.”

Have studios hit the point of sequel overload?

“I think you have to take each movie for its own value. There will be those you’ll roll your eyes over and others you can’t wait to see,” said Carrie-Anne Moss, who returns in “The Matrix” sequels. “It all has to do with the intention. If someone’s intention is just to make money and exploit something for profit, then it’s not good. If it’s thoughtfully done, the proof’s in the pudding.”

Actors can be reluctant to return and characters often wear out their welcome with audiences if sequels become too repetitive. Sometimes, a new twist can reinvigorate a franchise.

This summer’s “American Wedding” tries that by reuniting most of the “American Pie” gang for the nuptials of Jason Biggs’ and Alyson Hannigan’s characters.

Actors, from left, Arnold Schwarzenegger, Nick Stahl, David Andrews and Claire Danes appear in a scene from Warner Bros. Pictures' Terminator

“I wasn’t really interested in doing something that would just be ‘American Pie 3,”‘ Hannigan said. “We still do have the elements that made the first ones work, the gross-out humor and the heart. But people who would have been groaning, ‘Don’t do a third one,’ I think they’ll be happy, because there’s a different story line, which is a wedding.”

Before 1980, any given year might produce only two or three sequels. The number generally rose through the 1980s, with box-office tracker Exhibitor Relations counting 19 sequels in 1990.

It has ebbed and flowed since then, with the number of sequels and prequels falling to nine in 2001 then shooting up to 19 again last year and 25 this year, according to Exhibitor Relations’ Paul Dergarabedian.

In the 1970s and early ’80s, “Star Wars,” “Jaws,” “Rocky,” “Superman” and “Star Trek” were among franchises that kicked sequels into high gear.

In those days, sequels often were inferior knockoffs resulting in dwindling box-office returns for successive movies. The franchises generally were turned over to lesser filmmakers, and key cast members often did not return.

Studios have learned that keeping the cast and director intact, along with much of the support team, can result in well-tailored sequels whose revenues approach or exceed those of the originals.

“If you think about your favorite television series, the first episodes often aren’t very good at all. They’re just getting their feet wet,” said “Spy Kids” and “Desperado” creator Robert Rodriguez, who has sequels to both franchises due out this year, “Spy Kids 3-D: Game Over” and “Once Upon a Time in Mexico.”

“If you get the original creative team back on a film, they can really fine-tune what they tried to do with the first one, and instead of making a cheap, quick knockoff, actually make a better sequel out of it.”