I think if you have a job that gives you the chance to expand your skills, pick new tech with the ability and time to learn onsite, and offers you that grace, that's a great company to work for.

Within my power I try to do that with my directs, making sure new interesting things are cycled in so their CVs become stronger. But me, personally, I've had really bad luck with this. I always had to study on the weekends for something that either isn't used in my company or someone else jealously guards because it's hot on the market.