Spin Doctor - S1-E15
Continuity mistake: Nick takes to the air wearing a blue windbreaker, but lands wearing a long black duster coat. (00:14:05)
Spin Doctor - S1-E15
Factual error: Nick tells Nat about his past life as an assistant professor in the U.S., and refers to himself as "a certain indigenous vampire." Nick wasn't indigenous (native) to either the US or Canada, where the show was set. He came from Brabant, now part of Belgium. They were probably trying for "itinerant" (wandering), which would accurately describe Nick's long life.
Answer: Nick was sick and tired of being an immortal bloodsucker. He wanted to be human, fall in love, get married, have children, grow old and die. As for Janette, according to her, she fell in love and the passion she felt "cured" her of her blood lust.