DURATION OF H-1B STATUS
Once I receive my H-1B visa, what is the duration of H-1B status? Initially, you may obtain H-1B status for up to three years. Prior to the expiration of the three-year period, you may apply to extend your stay for an additional three years. In general, at the end of the six-year period, no further extensions of H-1B status are permitted. Although you are allowed to change employers by submitting a new petition to USCIS (accompanied by a new LCA from DOL), this does not waive the six-year limitation.
Extensions after six years are possible for certain persons who have experienced lengthy delays in the adjudication of their applications for labor certification or for employment-based visa petitions, or for H-1B holders who are unable to adjust their status in the U.S. because of backlogs in their preference category.
Therefore, if you wish to apply for lawful permanent residence, you should begin this process as early as possible after you have located satisfactory employment.