Goldstick told The Hollywood Reporter that since the show is based on a book series, the producers have to "stretch" the material out.
He said: "We knew as a television series that Warner Bros would want several seasons, ABC Family as well, and therefore we have to parse out information and figure out how to pay allegiance to the books and deploy the plot points that are there, but also build on things that aren't there."
Goldstick added that the producers are currently planning to reveal the identity of 'A' in the final episode of the show.
"And maybe some series aren't meant to go beyond four seasons," he said. "This could be a four-season show. In the world we live in now, some things can live on for 12 seasons, some [things] are really meant to be delicious for three, four, five seasons. It doesn't mean they aren't successful, it means they told the story they needed to tell."
Goldstick suggested that Pretty Little Liars is "probably" a show that would benefit from a shorter life but joked that he will "get in trouble" for saying that.
"Watch, the fifth season will be completely recharged," he said. "By the fifth season, maybe something happens that re-energises the series and you go, 'Oh my God, this character has brought an entire new energy and now we have a whole other story to tell'."
The second season of Pretty Little Liars premiered last night and continues on Tuesdays at 8/7c on ABC Family.
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