You may see a prompt like this:
This means that your machine is not turned on and connected to the Internet at night.
The Celeratec eProActive Management Agent which maintains your system is programmed to apply updates and complete regular system maintenance between 1AM and 3AM every night.
If your machine is always off during this timeframe, then at some point when your machine is very delinquent, it will be forced to complete these tasks during the workday, slowing your computer and forcing you to reboot.
To avoid this, consider leaving your machine online and connected at night.
If you can only leave your machines on occasionally, plan for Tuesday night, since this is when Microsoft releases updates, but more nights are better.