By default, if your
BlackBerry smartphone isn't connected to a power outlet and your smartphone
and the other devices that are connected to your mobile hotspot are inactive for 15 minutes, Mobile Hotspot mode turns off automatically to conserve battery power.
On the home screen, click the connections area at the top of the screen, or click the Manage Connections icon.
Click Networks and Connections >
Mobile Hotspot Connections >
Auto Shutoff Timer