The 27-year-old was set to enter free agency at the end of the 2015 season before agreeing to a new deal with the rising Kangaroos.
“The club wanted to get it done and I was happy to agree,” Swallow told News Limited.
“It’s an extra three years. I’m 28 this year which takes me to 30, 31 which I’m happy about.
“Depending on how we’re going, I’d be happy to pull the pin then, or if I’m still loving it, I’d keep going.”
Swallow missed 10 months of action after rupturing his Achilles tendon during the 2013 season, returning in May last year to join a bolstered midfield featuring star recruit Nick Dal Santo.
After shaking off the rust following major surgery, he managed 21.9 disposals per contest in 18 games, his lowest output since the 2010 season, en route to a preliminary final appearance.
Swallow accepted a modest new deal to ensure the Kangaroos have the best possible chance of remaining competitive and adding talent over his peak seasons, a running trend among the club’s better players.
“I don’t think we’ve ever sat down as group and said let’s all take a pay cut,” he said.
“A lot of our guys aren’t driven by money.
“Look at Toddy Goldstein, I would’ve thought other clubs would’ve chased him, but he loves North Melbourne. The blokes love the footy club.”
The Kangaroos have a number of key players who could still hit the open market when free agency rolls around later this year, including Brent Harvey, Drew Petrie, Michael Firrito, Nathan Grima, Robbie Tarrant and Scott McMahon.
Photo: Michael Dodge/Getty Images.