My wife and I skyrocketed in our careers. How? Between 1997 and 2008 we did exactly the opposite of what our parents recommended and kept hopping jobs. My longest stint at any one place was 18 months and hers was two years. When we realized that our skill sets were too expensive and rare to waste at a single project, we started our own consulting firm and continue to cycle through projects regularly.
Remember, whether you are self-employed or employed by someone else, you ultimately work for yourself. Act accordingly and guard your self-interests.