This can vary greatly depending on the breed and health of the bitch. They can have heat cycles for 10 years or more although breeding them at this age is not recommended.
Yes. The season that is on right now is the final season. However they have said that they plan on making a movie based on it, in which Jack will be killed.
No. The series was picked up for an eighth (January 2009) and ninth season (December 2009) by ABC after it was dropped by NBC.The series was announced as cancelled by ABC in May, 2010.