Once I receive a U.S. visa, how long am I legally allowed to remain in the country? I understand that the visa expiration date may not always match the duration of stay permitted by U.S. Customs and Border Protection at the port of entry — can you explain this difference? Are there conditions under which I can extend my stay, and what happens if I accidentally overstay? Also, does the duration of stay vary between visa types like B1/B2, F1, or H1B? What are the risks and consequences of violating stay limits?