He's clinging on just to get a record. He also left his family for 3 years to play in Toronto (only lasted two). Come on, let's not play this game: He went back to SJ hoping Wilson would do him a solid for all his years of service, almost certainly because no other GM would.
And now he's hoping a contender will pick up him when anyone who has seen him play the past couple of years will tell you he's no longer an NHL player.
As for me telling Marleau when to call it a career, of course it's not my place, but lets just see what happens over the next few weeks - if he gets his wish and a contender takes him on, and he actually plays more than 5 minutes a night, then apparently someone thinks he can still play.