I'd probably be comfortable with 4 years on the expectation that you might end up eating a bad year at the end of the deal. He's 32 right now and while he only has about 700 IP in his MLB career, he also has close to 1200 IP from his time in NPB (though he wasn't like some crazy Daisuke Matsuzaka overwork candidate, having an average of like 25 starts and 160-170 innings per NPB season. His 2023 with the Jays was the second highest inning total in a season after only his last year with Seibu before joining the Mariners.) so I'm not sure I'd want to commit like 5-7 years on him since he is a velo guy and not a crafty, Maddux-esque control pitcher who stands a better chance of aging well.
That probably wouldn't be enough though. Some team is going to figure he'll pitch fine until he's 37-38 and give him 6 years.