I had win 8 for a short time before upgrading to 8.1, and I never run the built-in defrag, not even when I had Vista and win 7.
If you want to "witness" the progress of defrag and optimization, may I suggest using the followings.........
1. Auslogics for disk defrag
2. CCleaner for disk cleanup, removing temp files, cookies etc etc.
That is what I use since the days of Vista.
I am using 8.1 Pro now. I suppose what I say from here on will be applicable to your Win 8.
Defrag and Optimization can be and supposed to be done at scheduled time. User shouldn't have to do it manually. You can set up the schedule.( see my screenshot)
I have just finished, for the first time, using the defrag and optimize app and here is the result....
