Question: How long was Patrick Swayze and  an American actress , who stared in a 1987 American post-apocalyptic science fiction action film, married?

Context paragraphs:
Steel Dawn: Steel Dawn is a 1987 American post-apocalyptic science fiction action film that mixes the genres of science fiction and western.  It stars Patrick Swayze and his wife, Lisa Niemi.

She's Like the Wind: "She's Like the Wind" is a 1987 power ballad from the film "Dirty Dancing", performed by Patrick Swayze.  Though Swayze is the primary vocalist on the single, it was billed as being performed by "Patrick Swayze featuring Wendy Fraser"; Fraser is heard throughout much of the song, specifically in the final chorus.  The single reached number three on the "Billboard" Hot 100 and number one on the Adult Contemporary chart.

Lisa Niemi: Lisa Anne Haapaniemi Swayze DePrisco (born May 26, 1956), also known by her stage name, Lisa Niemi, is an American writer, director, actress and dancer.  She is the widow of actor, singer, and dancer Patrick Swayze.  They were married for 34 years, from 1975 until his death in 2009.

Revolution (TV series): Revolution is an American post-apocalyptic science fiction television series that ran from September 17, 2012 until May 21, 2014; it was cancelled by NBC in May 2014.  The show takes place in the post-apocalyptic near-future of the year 2027, 15 years after the start of a worldwide, permanent electrical-power blackout in 2012.  Created by Eric Kripke and produced by J. J. Abrams' Bad Robot Productions for the NBC network, it originally aired on Mondays at 10:00 pm (ET) doing well enough that NBC ordered a second season shortly after the first season finale.

Terminator Salvation: Terminator Salvation is a 2009 American post-apocalyptic science fiction war film directed by McG, starring Christian Bale and Sam Worthington.  It is the fourth installment of the "Terminator" film series.  In a departure from the previous installments, which were set between 1984 and 2004 and used time travel as a key plot element, "Salvation" is a post-apocalyptic film set in the year 2018, fourteen years after the events of "".  It focuses on the war between Skynet's machine network and humanity; the remnants of the world's military have organized as the Resistance, fighting against Skynet's killing machines.  Bale portrays John Connor, Resistance fighter and central character to the franchise, while Worthington portrays cyborg Marcus Wright.  Anton Yelchin plays as a young Kyle Reese, a character first introduced in "The Terminator", and the film depicts the origin of the T-800 (Model 101) Terminator, played by Roland Kickinger, who replaces Arnold Schwarzenegger as the title character, though CGI was used to recreate Schwarzenegger's facial likeness from the original film, with his consent.

Silent Running: Silent Running is a 1972 environmentally-themed American post-apocalyptic science fiction film starring Bruce Dern, featuring Cliff Potts, Ron Rifkin and Jesse Vint.  It was directed by Douglas Trumbull, who had previously worked as a special effects supervisor on science fiction films, including "" and "The Andromeda Strain".

Oblivion (2013 film): Oblivion is a 2013 American post-apocalyptic science fiction film based on Joseph Kosinski's unpublished Radical Publishing graphic novel of the same name.  The film was co-produced and directed by Kosinski.  It stars Tom Cruise, Morgan Freeman, Andrea Riseborough, and Olga Kurylenko.  The film was released in the U.S. on April 19, 2013.  According to Kosinski, "Oblivion" pays homage to science fiction films of the 1970s.

James Cameron filmography: James Cameron is a Canadian director, screenwriter, and producer who has had an extensive career in film and television.  Cameron's debut was the 1978 science fiction short "Xenogenesis", which he directed, wrote and produced.  In the early part of his career, he did various technical jobs such as special visual effects producer, set dresser assistant, matte artist, and photographer.  His feature directorial debut was the 1981 release "".  The next film he directed was the science fiction action thriller "The Terminator" (1984).  It starred Arnold Schwarzenegger as the titular cyborg assassin, and was Cameron's breakthrough feature.  In 1986, he directed and wrote the science fiction action sequel "Aliens" starring Sigourney Weaver.  He followed this by directing another science fiction film "The Abyss" (1989).  In 1991, Cameron directed the sequel to "The Terminator", "" (with Schwarzenegger reprising his role), and also executive produced the action crime film "Point Break".  Three years later he directed a third Schwarzenegger-starring action film "True Lies" (1994).

Waterworld: Waterworld is a 1995 American post-apocalyptic science fiction action film directed by Kevin Reynolds and co-written by Peter Rader and David Twohy.  It was based on Rader's original 1986 screenplay and stars Kevin Costner, who also produced it with Charles Gordon and John Davis.  It was distributed by Universal Pictures.

After Earth: After Earth is a 2013 American post-apocalyptic science fiction action film directed by M. Night Shyamalan, who co-wrote it with Gary Whitta, based on an original story idea by Will Smith.  It is the second film after "The Pursuit of Happyness" that stars real-life father and son Will and Jaden Smith; Will Smith also produced via his company Overbrook Entertainment, and the distribution was by Columbia Pictures.  The film takes place in the 31st Century, when the Earth has long been abandoned and humans have been in conflict with a mysterious alien race.  It tells the story of a high-ranking general in the peacekeeping organization Ranger Corps, and his son, who, after an incident during a spaceflight, find themselves fighting for survival on a hostile planet (which is Earth itself).

Supporting paragraphs: Steel Dawn Lisa Niemi
Answer: 34 years