My visa is expired/about to expire. What should I do?
An entry visa in your passport is relevant ONLY to your eligibility to be admitted to the U.S., not for remaining in the U.S. What matters while you are in the United States is maintaining your F-1 status for the duration of your academic program as reflected on your I-20. If your entry visa expires while you are in the U.S. you will have to obtain a valid one before re-entering the U.S. from a trip abroad. You cannot renew a visa in the U.S. but will have to apply for a new one at a U.S. consulate abroad, most likely in your home country.