The Fundamentals of Engineering (FE) exam, the first of two tests offered by the National Council of Examiners for Engineering and Surveying, is the prerequisite for receiving the Engineer in Training (EIT) credential (NCEES). Technically speaking, it never expires because passing the FE test essentially appoints the taker as an Engineer in Training.
However, given that one must register with and apply for the certification with the specific state's board of engineering before using the EIT credentials, certain jurisdictions may set their own expiration date criteria. For instance, the EIT certificate must be updated every eight years according to the Texas Board of Professional Engineers and Land Surveyors. Before enrolling with the NCEES and sitting for the FE test, it's also a good idea to verify with your state because there are some differences in the requirements for eligibility.