This is controlled by the ''WAIT_BEFORE_DISCONNECT'' site parameter which can be adjusted in your Site Administrator - Site Configuration tab. The default is 600 minutes (10 hours) but can be adjusted to as low as 60 minutes (1 hour).

    Parameter:
    WAIT_BEFORE_DISCONNECT

    Description:
    The time interval in minutes that the ALM client can be inactive before it is disconnected from the ALM server machine. Disconnecting the client enables the license to be used by another ALM user. By default, the value is set to 600 minutes. For performance reasons, it is recommended to set a value of at least 60 minutes. If you set the value to -1, ALM is not disconnected, regardless of how long the client is inactive.