Sinclair, of Windward Close, Enfield, was cleared of murder in October, but was convicted of manslaughter.
Mr Sinclair, a driver for a church care centre, was scared of his wife who had attacked him before, the court heard.
Judge Stephen Kramer told dental nurse Sinclair: "I am satisfied you are a domineering person - particularly when you have taken drink."
The court heard she had robbed Mr Sinclair's family and friends of "a much-loved and respected man".
Ahmed Youseff Work colleagueI lost count of the number of injuries. He always had an injury”
Later, when they argued about what to watch on TV, she stabbed him in the back of his left thigh.
PC Gillian Bills said Sinclair told her on the way to hospital: "We had an argument about what to watch on TV.
"He wanted to watch football and I wanted to watch Harry Hill."
'Bogus scene' Sinclair, who had been been married twice before, had denied stabbing her husband and claimed he was injured on a broken wine glass.
She said the 73-year-old must have stabbed himself by accident when he got her into a headlock and they struggled.
She told the court they were introduced in May 2008 and found an attraction, despite being "like chalk and cheese".
"We used to go out every evening. We'd go on holidays and trips. We had fun," she said.
But Bobbie Cheema, prosecuting, said she had set up a "sham, bogus scene" while her husband lay dying.
Miss Cheema said Sinclair was violent to her husband and his and family and friends noticed the injuries.
Mr Sinclair, who had four grown-up children, had told his son Vincent that his wife had broken his arm.
His work colleague Ahmed Youseff had told the court: "I lost count of the number of injuries. He always had an injury."
Metropolitan Police officers had been called by the ambulance service after reports that Mr Sinclair had been injured at his home. He was taken to hospital where he died the following day.
Det Insp Ken Hughes said after the case: "I would like to pay tribute to Mr Sinclair's family who have dealt with this tragedy with great dignity and grace.
"I hope the sentence offers them some comfort and enables them to move on with their lives."