An (ISC)2 CISSP certification is valid for three years in total. It is possible to retake the course and exam, or you can earn and submit 120 Continuing Professional Education credits (CPEs) during the three years.
CPE credits are earned by participating in Continuing Professional Education activities. To maintain certifications, you can earn and submit the minimum number of credits required to maintain your certification. The minimum number of CPE credits required to maintain the validity of a CISSP certification is 120 over three years.