You can edit the Device Activity Timer setting yourself in Company Profile > Settings, see the screenshot below:

You can customise the length of the timer to any duration you want between 1 hour and 16 hours. 

This will update all devices with the device activity timer within your account, so check the duration is suitable for the majority of device users. 

We recommend that timers are not set to expire outside of working hours. Timed activities that expire out of working hours take longer to close due to work mobiles being switched off or escalation contacts not being available to answer calls from the Alarm Receiving Centre (ARC).