Dear Universal, Vin Diesel, & Family,

A plea. After eight films and $4.4 billion and counting, it’s time for the “Fast and the Furious” series to eye the exit ramp. I’m not saying you have to send Dom Toretto into the great garage in the sky without giving him and Letty and Hobbs and the Shaw brothers and whoever it is that Scott Eastwood plays, a proper sendoff. There’s still plenty of gas left in the series’ tank, especially after “The Fate of the Furious” just shattered records with a $532.5 million global opening. I just hope you understand the importance of the old adage to leave the audience wanting more.

After all, nothing is sadder than a film franchise that should have ended several installments ago. Just ask “Die Hard,” “Lethal Weapon,” “The Expendables,” or even “Indiana Jones.” It would be so sad to see an arthritic Dom slide behind the wheel of the latest muscle car.

Wrapping things up is not just about avoiding the inevitable ravages of age. A graceful exit is all the more essential because no series in history has been so successful at reinventing itself over such a long period of time. What began as a B-movie, “Point Break” knockoff about a government agent infiltrating a band of hard-driving criminals, morphed into a family drama, a heist adventure, a globe-spanning thriller, and whatever other genre was currently in the zeitgeist. Through it all, “Fast and Furious” cleverly injected fresh blood into the series, introducing Dwayne Johnson and Jason Statham into the proceedings, and providing a jolt of adrenaline with each new cast member. The willingness to keep changing the tires is what enabled the franchise to avoid a straight-to-DVD fate. Bonus points for recognizing before nearly any other major studio did that having a multi-ethnic cast boosts the box office — inclusion isn’t just a good thing, it’s good for business.

Not everything has been a victory lap. The filmmakers also had to grapple with the unimaginable. After Paul Walker died in 2013 in a horrific car accident, Universal and the filmmakers would have been forgiven for scrapping “Furious 7” entirely. After all, Walker hadn’t completed his work on the sequel. Instead, using digital wizardry and stunt doubles, they were able to transform the movie into a fitting memorial for the fallen star, giving his fans a chance to honor his work and tastefully allowing for his character to live on in perpetuity through the magic of cinema.

Show that same courage now. Here’s the thing, domestically, at least, the “Fast and Furious” series appears to be tapering off. “The Fate of the Furious'” $100.2 million launch is a far cry from “Furious 7’s” $147.2 million bow. It’s the first time that a “Fast and Furious” film hasn’t improved on the opening of its predecessor since 2006’s “Fast and the Furious: Tokyo Drift.”

Reviews were noticeably more downbeat, with some ranging on hostile. The films’ overall revenues are growing on a global basis, thanks to China, where “The Fate of the Furious” roared to a massive $190 million debut. But U.S. studios only get 25% of those ticket sales, roughly half of what they earn in the States — that means they’ll have to bring in twice as much in the Middle Kingdom to make the same amount they earn domestically.

As each sequel gets released, the price tag balloons. Stars demand more money and a greater share of the spoils. “The Fate of the Furious” cost $250 million and change to produce, that’s a big jump from the last installment’s $190 million price tag and huge increase from the first film’s $38 million budget. Such is the gravitational trajectory of a film franchise that with every new chapter the costs climb and the profits shrink.

Then there’s a nagging sense that a company that used to pride itself on being an on and off-screen family, is fraying under the strain of global superstardom. “The Fate of the Furious” was dogged by reports of a feud between Johnson and Diesel, one that resulted in Johnson taking pot shots at unnamed “candy a–es” on social media. Despite Diesel’s lead-footed attempts to play down the tension, the two actors appear to loathe one another. Johnson skipped the film’s CinemaCon presentation, its foreign premieres, and made only a perfunctory stop on the red carpet of its New York launch — seriously, the man channeled Usain Bolt as he went down the press line. This is a group of actors that’s looking dangerously close to the 2004 U.S. Olympic basketball team, a band of superstars that lacked the chemistry to deliver the gold.

Here’s the thing, endings are good. Just look at “Girls” or “Breaking Bad,” two television series that got better and better as they raced toward preordained finales. Great dramas wrap things up, otherwise Oedipus would still be shtupping his mom.

In a recent interview with Variety, screenwriter Chris Morgan said he has a clear idea of how he wants the franchise to fade out. Knowing how this story ends, and signaling to viewers that the filmmakers are racing toward a conclusion, could give this series the kind of energy it needs to finish the race strong. For his part, Diesel has described “Fate of the Furious” as kicking off a new trilogy. He should consider rolling credits after part 10. It may mean leaving some money on the table, because the crew could probably chug along for eight more sequels and ever-diminishing box office returns, but it’s better to go out on your terms. Otherwise, the audience may eventually decide to stop showing up.

Yours,

A Faithful Box Office Analyst

P.S.: For the love of God, don’t have this series go into space.

P.P.S.: Seriously, have you seen “Moonraker”?