Amazon SDK - Temporary Credentials and AssumeRoleRequest

You can make use of GetSessionToken, which accepts the DurationSeconds value as high as 129600 provided you are an IAM user.

From the docs:

Credentials that are created by IAM users are valid for the duration that you specify, from 900 seconds (15 minutes) up to a maximum of 129600 seconds (36 hours), with a default of 43200 seconds (12 hours)