The validity of a U.S. work visa depends on the specific category and the agreement between the U.S. and your nationality. Generally, visas like H-1B are issued for three years with extensions possible up to six years. L-1 visas are typically valid for one to three years initially, with a maximum stay of five to seven years depending on the role. O visas are granted for the duration of the event or project, usually up to three years, while TN visas for Canadian and Mexican professionals are valid up to three years. Extensions are often possible if requirements remain met.