I've always been of the mindset that you should work hard to the last day as a point of personal pride. Plus, word gets around and it only helps your profile in a very competitive industry. 

I well recall stories out of CFTR in the final days of Brady in the Morning, where Jim Brady was told a good 6 months or so beforehand that they weren't going to renew his contract. He did a serviceable job for that half year, but if you've ever heard those shows, you can tell his heart wasn't in it, and he didn't go that extra mile to make his show entertaining. Time, temperature, record intros and extros, the occasional one liner and that was it. No creativity and no effort. 

I liked the guy and knew him, but I was surprised when he did that. He must have felt let down and somewhat bitter, since he'd helped take the station to #1 and finally beaten CHUM. I was also kind of stunned that management left him on the air to partially tank the all-important morning shift. Not a great outcome either way around.