As a recruiter, a large portion of my time goes into reviewing resumes, sending them to clients, and responding to their questions regarding a prospective candidate's employment history.
"Why have they had five different positions for five different employers in the last two years?" "Why can't they last at a job for more than a month?" And more often than not, those questions are rhetorical, a means of making a point. What point is this exactly? The point is that companies want to see stability in future hires.
Why is stability so important? The reason is that hiring, training and retaining talent comes with a cost that companies would prefer not to invest in for short-term employees. Instead, they hope to hire someone who will last long enough to make up for these on-boarding costs and add additional value.
So, how long is long enough? According to experts, you should stay at your place of employment for a minimum of two years. It's enough time to learn new skills and build your qualifications, while short enough to show that you value growing in your career.
You can't always keep from leaving a position before the two year mark. Sometimes, you will just have to go ahead and get on out, but keep in mind that a string of exes looks bad in both relationships and employment. Be prepared to weigh the consequences and to consider how the move can adversely affect your future employment prospects before you hop on out.