Question: How long have the authors of the book series with the fictional protagonist Fiddler been married? 

Context paragraphs:
The Kindly Ones (Littell novel): The Kindly Ones (French: "Les Bienveillantes" ) is a historical fiction novel written in French by American-born author Jonathan Littell.  The book is narrated by its fictional protagonist Maximilien Aue, a former SS officer of French and German ancestry who helped to carry out the Holocaust and was present during several major events of World War II.

Veronica Mars (character): Veronica Mars is the fictional protagonist, occasional narrator (through voiceovers), and antiheroine of the American television series "Veronica Mars", which aired on UPN from 2004 to 2006 and on The CW from 2006 to 2007.  The character was portrayed by Kristen Bell through the duration of the series.  Following the show's cancellation, Bell reprised the role in the 2014 film continuation.  The character, created by Rob Thomas, was originally male and the protagonist of his unproduced novel "Untitled Rob Thomas Teen Detective Novel", which eventually became the basis of the series.  After the work's transition from novel to television series, Thomas changed the character's gender from male to female as he believed a noir piece told from a female point of view would be more interesting.

Chu Liuxiang: Chu Liuxiang is the fictional protagonist of the "wuxia" novel series "Chu Liuxiang Series" (楚留香系列 ) by Taiwanese writer Gu Long.  His given name "Liuxiang" literally means "lingering fragrance".  He steals from the rich to help the poor and upholds justice in the "jianghu".  He is nicknamed "Dao Shuai" (literally "Chief of Bandits/Thieves") or more popularly, "Xiangshuai" (literally "Chief Xiang").  He is intelligent, observant, kind and compassionate.

Ann Maxwell: Ann Maxwell (born April 5, 1944 in Milwaukee, Wisconsin), also known as A.E. Maxwell and Elizabeth Lowell, has individually, and with co-author and husband Evan, written over 50 novels and one non-fiction book.  These novels range from science fiction to historical fiction, and from romance to mystery to suspense (Evan, exclusively, has covered all kinds of crime - from local to international).  Ann and Evan have been married for over 40 years.

Lu Xiaofeng: Lu Xiaofeng is the fictional protagonist of the "wuxia" novel series "Lu Xiaofeng Series" (陸小鳳系列) by Gu Long.

Robert Langdon (book series): Robert Langdon is a fictional protagonist of a series of novels, novellas and short stories by American author Dan Brown.  A Harvard University professor of religious iconology and symbology (a fictional field related to the study of historic symbols, which is not methodologically connected to the actual discipline of semiotics).  Brown's novels that feature the lead character Robert Langdon also include historical themes and Christianity as motifs, and as a result, have generated controversy.  Brown states on his website that his books are not anti-Christian, though he is on a 'constant spiritual journey' himself, and says that his book "The Da Vinci Code" is simply "an entertaining story that promotes spiritual discussion and debate" and suggests that the book may be used "as a positive catalyst for introspection and exploration of our faith."

Hannah Britten: Hannah Britten is a fictional protagonist in the American police procedural drama television series "Awake".  She is portrayed by Laura Allen.  The character first appeared in "Pilot" and last appeared in the series finale "Turtles All the Way Down".  Hannah was created and designed by series creator and executive producer Kyle Killen after he created and developed the series "Lone Star" for the Fox network.

Fiddler (mystery series): Fiddler is the fictional protagonist in an eight book mystery series by A.E. Maxwell (husband and wife writing team Evan and Ann Maxwell, who also writes as Elizabeth Lowell.)  The books in the series are "Just Another Day in Paradise" (1985), "The Frog and the Scorpion" (1986), "Gatsby's Vineyard" (1987), "Just Enough Light to Kill" (1988), "The Art of Survival" (1989), "Money Burns" (1991), "The King of Nothing" (1992), and "Murder Hurts" (1993).  Fiddler is an independently wealthy Southern California resident with a past who occasionally solves crimes with the assistance of his ex-wife and on-again, off-again lover Fiora Flynn, a successful investment banker.  Themes included action and adventure with villains ranging from KGB officers and Colombian drug smugglers to high society artists and corporate executives.

Drake Maijstral: Drake Maijstral is the fictional protagonist of a series of science fiction novels by Walter Jon Williams.  He appears in "The Crown Jewels" (1987), "House of Shards" (1988), and "Rock of Ages" (1995) (collected as "Ten Points for Style" by the Science Fiction Book Club).

The Flashman Papers: The Flashman Papers is a series of novels and short stories written by George MacDonald Fraser, the first of which was published in 1969.  The books centre on the exploits of the fictional protagonist Harry Flashman.  He is a cowardly British soldier, rake and cad who is placed in a series of real historical incidents between 1839 and 1894.  While the incidents and much of the detail in the novels have a factual background, Flashman's actions in the stories are either fictional, or Fraser uses the actions of unidentified individuals and assigns them to Flashman.  Flashman is a minor character in the 1857 novel by Thomas Hughes, "Tom Brown's School Days"; Hughes' version of the character is a bully at Rugby School who is expelled for drunkenness.  The character was then developed by Fraser, and appeared in the 1969 novel "Flashman".  Fraser went on to write a total of eleven novels and one collection of short stories featuring the character.

Supporting paragraphs: Fiddler (mystery series) Ann Maxwell
Answer: over 40 years