In general, a physician can hold H-1B status for a maximum of six consecutive years. Initially, the H-1B petition may request a maximum of three years for any particular job.  After that, an extension request must be filed that can extend the H-1B for another three years, if necessary. Nevertheless, an H-1B worker may not extend their stay beyond six years by simply switching employers. Consider the following example:

An H-1B physician works for Employer A for three years. He then enters into a five-year contract with Employer B.  In this case, the physician will not be able to serve out the last two years of his contract with Employer B in H-1B status because he will have exceeded the six-year maximum time period for this visa.  However, if at any time during this period, the H-1B employee remains outside the U.S. for one year or more, a new H-1B admission period begins and he can hold H-1B status for another six years.

Extensions of H-1B status beyond the six-year limitation are available where the employee has a petition for immigrant worker (I-140 petition) or a labor certification application with the Department of Labor that has been pending for more than 365 days. In this case, H-1B status may be extended for one-year periods.  In addition, if the employee has an approved I-140 petition but cannot be approved for permanent residence because of an immigrant visa backlog, H-1B status may be extended for three year periods.

Finally, any request for an H-1B extension with the same employer must be filed before the current H-1B status expires.  The filing of the H-1B extension request automatically extends H-1B status for 240 days while the USCIS processes the request.  This means that the employee may continue to work although the extension request has not yet been approved.  For example, let's suppose that a physician's H-1B status is set to expire on April 30, 2012.  So long as the employer files an H-1B petition for an extension on or before April 29, 2012, the physician may continue to work for the employer for another 240 days without an approved extension request.  At the end of this 240-day period, the physician will be out of lawful status unless the extension request has been approved.  In all likelihood, however, the extension request will be decided in less than 240 days.