Nat-Test and JLPT are among the popular Japanese language certificates chosen by many. While there is no specified validity period on the certificates, some employers may require certificates to be valid for around 2-3 years. This is not because the certificates lose value after that time, but to ensure that candidates still maintain their Japanese proficiency and can adapt to modern work environments. Therefore, the 2-3 year validity period is just to assess the learner's competency. If you can demonstrate that your Japanese language ability remains strong as indicated in the certificate, you can still be recognized even if the certificate was issued 5-10 years ago.