The visa stamp in your passport at the U.S. Consulate is for permission to enter the United States for a specific purpose and period of time. Students are usually given an F-1 visa. Spouses and children of F-1 visa holders are assigned an F-2 visa. Since this stamp is only important for entry or re-entry into the U.S., there is no need to worry if it expires while you are here. If you plan to leave the U.S. temporarily, the International Student Services Office will counsel you on how to obtain a new visa.