To save power, the computer goes to sleep after a short period of inactivity.
I set: Never (PC) and Never (Disk)
but for some 
unspecified reason, and so again changes, eg. for 2 hours or less  

Simply prevents computer from going into standby or sleep mode to keep 
Repair Active !!! 

Prevent standby/sleep when Tweaking Windows Repair Start RepairStarting Repairs...
   Started at (20-04-16 10:08:58)
Unhide Non System Files
   Start (20-04-16 10:08:59)
   W:\ - Total Files Unhidden: 0 out of 397483300 searched. - Check Unhidden_Files.txt for list of files unhidden
   Done (20-04-16 10:32:03)
Cleaning up empty logs...
All Selected Repairs Done.
   Done at (20-04-16 10:32:03)
   Total Repair Time: 00:23:06
...YOU MUST RESTART YOUR SYSTEM...