An extension of a visa is not automatic. It must be extended a failure of which, the alien would be considered to have overstayed and out of status. This leads to the 3 year or 10 year bar and hinders the alien's stay or return to the US in future.
It is very important to apply for the extension of the visa before it expires to ensure that the alien is still lawfully in the US. It is also advisable to file for the extension within a 30-45 days of the visa expiring.
In the event that your authorized stay has already expired and you are late in filing for an extension, an application may still be made in the event all of the following is true: