For assuming one role it can be up to 12 hours. If you're doing role chaining like the parent mentioned (where the 1st assumed role then assumes a 2nd role) then the maximum session duration is 1 hour. AWS has this documented here:
https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_te...
> Role chaining limits your AWS CLI or AWS API role session to a maximum of one hour.