My parents worked at the same place their entire lives...I seem to have to find a new job every 9-10 years...
I'm closer to every 4 - 5 years looking for a new job. I look at it like this, I expect, based on hard work, that I get a promotion every 18 months to 2 years. If that can't be supported by my employer, than after no more than 3 - 4 years I look for a better position with another company. My career field, Information Security, is exploding. I started on the low end of things a few years ago and am at an intermediate level now. In the next year or so, I should be able to get a Sr. level position, if not with my company, than with another. I will work hard for a company when I'm employed by them, but with no retirement benefits to speak of, either the company does well by me, or I can do well by another company.