I have a VIII Hero MOB with 6700K, M.2 950 Pro 256GB , 980 TI, 3200MHZ TridentZ 32GB Mem (8GB x4), Win 8.1 and Watercool and it boots in ~10-15 from a cold start.
I did Not change any setting in bios and i have not done any windows startup maintenance yet. This is a fairly new PC built within the past month and only have a game installed
on the 2nd HDD (Not on the M.2 950 pro) and i have a few monitoring programs installed on the 950 pro and all the standard OS stuff like Chrome Anti virus etc.
I think i can reduce the time by 3 sec or so if i lower how long the logo stays on in order to get into bios "F1/delete" etc. Probably can reduce it down to 1 sec rather then 3 sec that
its defult is set to.
So without doing a reboot right now to get the exact number its ~ 8sec to get to the asus logo then ~13 to boot to desktop from the Asus logo.
Hope that gives you a better idea.
However maybe a little advice, though i should be the last one to give any as iam fair from a PC pro. So any adivce i give will be more
so to check on something rather then do anything.;) It could be that your computer bios setting say for the Memory if set
to XMP mode and it is not happy and its restarting a few times while you may think that everything is just booting up and you are confusing the 2.
I have seen this before on another PC with XMP ON it would do this weird On/off Cycle 3 or so times before it boot up to desktop. Which took ~2 minutes.
Once i updated the bios on that machine and re set it to XMP again it never had that problem again and booted up fast like my PC as i first mentioned above.
Prior to this it would sometimes bootup fast ~13 sec and other times ~2 minutes.
Make sure your PC is not actually restarting and you are confusing it with a normal startup.
Probebly not the issue but i mention it anyway just encase.:)