How long is my organ donor card good for at the organ bank, do I ever need to renew?

Forever and YES. As long as your organ donor card is available and there is no evidence to the contrary, your wish to donate will probably be honored. If you have an organ stamp on your drivers license, make sure that you continue to check the organ donor box every time you renew your license.
Variable. It varies according to state law. You can check with your local organ procurement organization.