WE’VE finally come to the end of the road with the Fifty Shades series, the trilogy of movies — based on E.L. James’s best-selling Twilight fan fiction — which has earned nearly $1 billion so far at the box office with its titillating promise of S&M-tinged erotica.

Friday marks the release of the final instalment, Fifty Shades Freed, the weakest of the movies, which will no doubt still rake in money from female audiences looking for Galentine’s Day amusement. One last time, they’ll be able to see Anastasia Steele (Dakota Johnson) explore, with wide-eyed alarm, the various gadgets that her now-husband Christian Grey (Jamie Dornan) keeps in his “playroom” for sexy time.

And what, if anything, have we learned from this trilogy? Other than some flogging techniques, a few surprisingly important lessons.

Audiences were here for this

It feels like beating the same old drum to say — once again — that women buy movie tickets and that studios would be wise to cater to them more often, but here we are. Fifty Shades of Grey was yet another example of the female demographic boosting box office. When the movie came out in Feb 2015, it made $85 million in its opening weekend, more than double what the heavily marketed, more dude-centric action flick Kingsman: The Secret Service earned. Fifty Shades went on to pull in $571m worldwide, which is quite something for a movie with a $40m budget.

Of course, the film already had a built-in audience. British author E.L. James’s painful prose didn’t hinder her first novel from becoming a megahit. The book was dubbed “mommy porn” by the media, which certainly underestimated the broad appeal of its tale of a virginal college student who falls hard for a studly and utterly personality-free Seattle billionaire with certain predilections.

Authors shouldn’t necessarily be in charge of adapting their own work

Fifty Shades of Grey the movie was remarkable simply because it was so much better than the book, which was replete with embarrassing asides from Anastasia’s “inner goddess”.

Director Sam Taylor-Johnson and screenwriter Kelly Marcel transformed the source material into something more tongue-in-cheek. It was hardly a perfect movie with its lack of chemistry between the leads, but it was disarmingly entertaining, not to mention streamlined.

Making the movie was not a good experience for Taylor-Johnson and Marcel, however. Production was a constant battle between the director and James. In an interview with Hollywood Reporter, Taylor-Johnson called the making of the film “an incredibly painful process”, because the two never seemed to see eye-to-eye.

Marcel, meanwhile, didn’t make an effort to see the film. “My heart really was broken by that process,” she said in 2015 on Bret Easton Ellis’ podcast. “I just don’t feel like I can watch it without feeling some pain about how different it is to what I initially wrote.”

The movie was the biggest stateside opening for a female director to date — although it’s since been surpassed by Wonder Woman — yet Taylor-Johnson wasn’t asked to return for the second or third instalments. Instead, James’ husband, Niall Leonard, adapted the sequel screenplays while James Foley took over directing duties.

The loss of Taylor-Johnson and Marcel was stark. The second and third movies take themselves much more seriously. Maybe there’s more sex but there are also more eye-rolling plot twists, not to mention bad pacing and cringey dialogue. Fifty Shades Darker still made plenty of money — $381m worldwide — but it didn’t keep pace with the first movie. The third instalment will most likely be the weakest at the box office, although it’s still tracking towardd a $30m-plus opening weekend.

Dakota Johnson can act

Nepotism is an epidemic in Hollywood, which means there are loads of people who aren’t entirely qualified for their high-profile acting/writing/fill-in-the-blank gigs, but beat out more talented commoners, anyway.

When Johnson was cast in Fifty Shades of Grey, the actress hadn’t done much outside of bit parts and a failed sitcom, although she had a pedigree: she’s the daughter of Melanie Griffith and Don Johnson. It seemed like a gamble to cast her in such a prominent role, but she turns out to be one of the movies’ greatest assets, bringing a down-to-earth vibe to her scenes despite whatever outlandish things are unfolding around her. Even within the constraints of more maudlin scripts during the second and third instalments, she brought humour to the movies.

That was a herculean task, considering how bad the dialogue could be, and Dornan couldn’t quite muster it. Although he’s been terrific in other roles, especially in the series The Fall, he never managed to elevate his character beyond slightly stalkerish, entirely wooden eye candy.

There’s no bad time to release a movie

The early part of the year is a wasteland at the theatres. The summer months offer a plethora of action blockbusters and, between Halloween and Christmas, we’re bombarded by awards hopefuls. But January and February promise little more than the dregs that didn’t make the cut the previous year.

That’s pretty short-sighted considering people need entertainment all year long, and the success of Fifty Shades speaks to that. The movies were all wisely pegged to Valentine’s Day, making them perfect for a date night for kink-curious couples or groups of unattached women looking for some steamy amusement.

—By arrangement with The Washington Post