Microsoft has a built in timer to reboot the WinPE bootdisk after 3 days. Microsoft's partner System Internals has a toolset for a work around.
From this link download the suite.
Pssuspend64.exe is the app you need for 64 bit bootdisk. Place this utility in User_Files (bootdisk creator does this with the add files tab.
Make a cmd file and include it in BootDisk_Scripts, below is its content:
cd /d %~dp0 set curDrive=%~d0 cd %curDrive%\User_Files\ pssuspend64.exe winlogon.exe pssuspend64.exe wininit.exe