It's been my experience that accepting whatever dumb challenge management presents is how you get kept on. The advice that "your job is to make your manager look good to his manager" rings true to me. I would add that boosting your manager's ego goes pretty far, too. I find both activities detestable, but necessary in corporate life.

Always keep interviewing. One of the biggest mistakes I’ve seen is stopping interviews after starting a new job, trusting in the company.

I've never understood how people can muster the energy for this. I'm sure it's a great idea, but I would burn out immediately.