College credits do not have a specific expiration date. However, each individual school or school system is free to set its own admission criteria, and it may consider credits in certain subjects such as science and technology to be too old to allow in some cases.
College credits in basic core requirements for general education are generally accepted by all colleges regardless of age, so long as they meet the school's accreditation requirements. Credits in specialized degree programs may become outdated in fields where information and needed skills change rapidly, however, such as degrees in scientific or computer fields. Schools may refuse to accept these credits or may ask applicants to take a test to ensure their knowledge is up to date.