In Hassan's case, he was extradited in November 2014. He was in prison in France until January 2018. During all this period, the investigative judge was still investigating the case. In January 2018, he said that he was not going to order a trial and Hassan was released. It took three years and two months.
I didn't review other cases regarding how long they stayed.
I wanted to mention that in Hassan's case, the case started in 2007 by a leak to a journalist, so he was under surveillance by the RCMP for a year. After a year, France requested his extradition. This is from 2008 until 2014, which was his extradition hearing. Then from 2014 to 2018, he was in prison. From 2018 until now have been the appeals in France.
This is not over, so it's going to take 20 years or so of one's life and the lives of children and other family members.