The requirements to renew your license vary state by state. For example, in New York, where I live, it's every three years. All I had to do was fill out a form and enter my credit card information, and it took less than five minutes. They can audit you to check you've actually kept up with your continuing education, but as you should be doing this anyway, it's not a big deal. Here's a little more information about the process: Licensure
You have to pay renewal fees. 30h of continuing education (they do not require a proof but can audit you any time). And if you get in some legal troubles, it may affect your license.