Craig Thomas confirmed that the show's team are writing the upcoming season eight "like it's the end", but added that they have "a plan A and a plan B going" if the long-running comedy is picked up for a ninth run, according to TVLine.
"It gets more and more difficult," co-creator Carter Bays said of the show's future. "It's going to be more and more work that we have to throw out if this isn't our last season. We'd like to know as soon as possible."
"We're going to need to know pretty soon," Thomas added. "[We're] approaching the moment where those two [plans] would diverge."
The pair claimed that wrapping up How I Met Your Mother after eight years would be "amazing", but insisted that they "absolutely" have enough material to produce an additional season.
"Wrapping it up in season eight would be amazing," said Thomas. "There's a part of us as writers that's drawn to that. It's exciting. We get to answer everything.
"Every episode of the season is so much more important because of that. [That's] something sort of thrilling and very nostalgic and sad to think about, but it'd be exciting to write."
Bays concluded: "If this is the last season… it's everything we ever dreamed of and more. Eight seasons is great. That being said, do we have a ninth season in us? Absolutely."
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> How I Met Your Mother Josh Radnor: 'Movies bring me balance'
How I Met Your Mother star Josh Radnor (Ted) recently admitted that the show's cast are uncertain if season eight will be the show's last.
"None of us know if the show is going to be ending this year or not," he confirmed. "I think the writers really need to know more than we need to know because they need to start either wrapping things up or keeping the story going."
How I Met Your Mother's eighth season begins on Monday, September 24 at 8/7c on CBS. In the UK, the series airs on E4.
Watch the cast of How I Met Your Mother discuss the new season below: