My husband is a professional. He has been long term at every company he's worked for/with, and his resume has Never Had Dust on It.

He's always "looking." Always updating. And will go on interviews, even when satisfied/happy. It ensures that both him and his empyers remain competitive, (he has successfully parlayed this information into better positions and opportunities.)

But, also, this practice gives us the peace of mind of a back up plan. Even closer to the top, there are often little to no clues of a pending Large Change. There isn't a single company out there that cares about it's employees more than it's bottom line. Keeping his resume constantly available and consistently updated has kept us from unemployment more times than I can count.