I use a scheduled task to run wpkg every evening, but use a script to generate a random start time as follows:

@echo off

rem Script to create a scheduled task to run wpkg

rem Random number between 0 and 59

set /a MIN=%RANDOM%/556

rem Prefix 0 to 9 with a leading 0

if %MIN% LSS 10 (
 set MIN=0%MIN%
) else (
 rem
)

schtasks /delete /tn WPKG /F
schtasks /create /sc daily /tn WPKG /tr "\\server\netboot\wpkg-0.9.10\wpkg-start.bat" /ru SYSTEM /st 01:%MIN%:00

I run this as a startup script via group policy, to the task is rescheduled at every boot.Joshua Weage, "creative ideas to spread out the running of wpkg installs?" SourceForge.net, 2007-07-19