Today, Amazon AppStream 2.0 announced the idle disconnect timeout feature. With this feature, you can automatically disconnect an idle user after a configurable period of time, ensuring your streaming instances are being actively used. Your user will receive a notification informing them if they are about to be disconnected due to inactivity. If your user reconnects before the separately configurable disconnect timeout period has elapsed, they will be reconnected to the same streaming session they previously had. If your user reconnects after the disconnect timeout has elapsed, or the separately configurable max session duration has elapsed, they will start a new streaming session. To configure the idle disconnect timeout feature for your fleets, see our documentation.

The idle disconnect timeout feature is available today at no additional charge in all AWS Regions where AppStream 2.0 is offered. AppStream 2.0 offers pay-as-you-go pricing. Please see Amazon AppStream 2.0 Pricing for more information, and try our sample applications.
 

from Recent Announcements https://aws.amazon.com/about-aws/whats-new/2019/05/amazon-appstream-2-0-adds-configurable-timeouts-for-idle-session/