One of my friends left for deployment and gave me his address. We haven't talked ever since because he doesn't go online or anything. Can his address or P.O. box ever change? Or do they stay with the same address for the whole deployment?

Also, how much would they charge? I've seen that on USPS they charge you like if it was local but I'm not sure... if I send a letter to a military address would it be just one stamp?

Thank you so much for your help!