In order to keep my users from getting windows update messages, I try to install any client updates at night. I have a few tricks to make this possible:
1: Boot up at night
Most computers can boot up automatically at night, using Wake-On-LAN. If your computer or its NIC does not support WOL, you can use the bios' power management to boot at night.
Don't start all computers at the exact same time, as this will result in a power peak - better spread it, like 5 computers per minute.