By default, OAuth 2.0 access tokens are valid for a maximum of 1 hour (3,600 seconds). However, the maximum lifetime for these tokens can be extended to 12 hours (43,200 seconds) according to the documentation: https://cloud.google.com/iam/docs/creating-short-lived-service-account-credentials#sa-credentials-oauth

This is currently not possible since the maximum 1 hour lifespan is hard-coded into both the ImpersonatedCredentials and the ServiceAccountCredentials class.