Hello,
To ease client computer performance issues, you can configure content downloads to run when client computers are idle. This setting is on by default. Several criteria, such as user, CPU, and disc actions, are used to determine when the computer is idle.
If Idle Detection is enabled, once an update is due, the following conditions can delay the session:
After one hour, the blocking set is reduced to CPU busy, Disk I/O busy, or no network connection exists. Once the scheduled update is overdue for two hours, as long as a network connection exists, the scheduled LiveUpdate runs regardless of idle status.
Check this Article:
Configuring client updates to run when client computers are idle
Hope that helps!!