In WSO2 API Manager, expiration period of all the access tokens is set to 60 minutes (3600 seconds) by default. However, you can modify the default expiration period value using identity.xml file located in <APIM_HOME>/repository/conf/ directory.
In the identity.xml file you can see separate configurations to modify default expirations of User tokens and application access tokens.
If you are planning to modify the validity period of appliccation access token, then you have to modify the default value of the <ApplicationAccessTokenDefaultValidityPeriod> element in identity.xml file. Changing the value of <ApplicationAccessTokenDefaultValidityPeriod> will not affect for existing applications which have alreday generated application tokens. So when you regenerate the application token, it will pick the token validity time from the UI. Therefore, for applications which has already generated tokens, token validity period needs to be changed from the UI as well. However, when you are creating a new application or when you generating the token for the first time, it will pick the token validity period from the identity.xml file.
If you are planning to modify the validity period of user token, then you need to update value of the <UserAccessTokenDefaultValidityPeriod> element in identity.xml file. The User token validity period will get updated when user generating and refreshing the token.