LemonJoy

There's two things that will degrade the cpu, one is heat and the other voltage. What is 'safe' is anyones guess right now as there isn't much data yet on what is failing. Having said that the general consensus seems to be about 1.4-1.45v core, 1.35-1.4v uncore and around 2.2-2.3 vrin. All depends on who you listen to. As such, if running high voltage and it doesn't boot one day well thats that with nobody to blame but yourself.
 
I'm running 1.35vcore (1.376v actual), around 1.2v uncore at the moment (bringing uncore up) and will quite happily push it to 1.35v - if needed, and vrin at just under 2.2v. If it dies in a couple of years so be it as new tech will be on the go. I think when you start failing at what 'were' stable settings and need to reduce voltage/multi it's time to tame things down if you want it to last.
 
IMO what you have is perfectly acceptable.
 
*EDIT - Even on IBT max i only go into mid 70deg. XTU under 70deg. That's with delid and custom W/C. The way i see it, no matter what voltage you're running, the lower the temps the better.

hmm yes, i found stability at least for 4 hours when increased cpu input voltage to 2.0
 
now i`m running intel extreme tuning utility
i5 4670k
vcore 1.340v 4700mhz
cache 1.280v 4400mhz
vvcin 2.0
 
max tems in Core Temp was 78c
 
this combo of 4700core and 4400cache showed best results in benchmarks,
example i could hit 8.06 in cenebench
with cache 4600 i  cant get more than 8.04.. i dunno why, 4500 showed same results
 
so i left cache at 4400 thus it uses lower voltage,
anyway to hit 4700 core with lower stable voltages i needed to increase vvcin to 2.0, will try lower it if i`m stable for 8h

again me, posting further results.
4670k and msi z87 g45
will try to lower volts, my temps about 70c~ in stress test
also OCed my ram (xmp profile let chose only 1600, i have those to work at 1866)
(hmm can`t upload any image in gallery.. any1 know why?)

core 4600mhz - 1.330v
cache 4400mhz - 1.310v
vvcin - 1.900v
 
btw at cache 4200mhz can keep it at 1.210v and core 1.220v at 4400mhz, tems 60c~ 
dunno if 200mhz worth it

in bios when u click with mouse on auto table of mhz`s appears, select 1333, 
i tried set clock from auto to link ans made it 9-9-9-24 (by manufacturer)
then changed volts to 1.5 in bios it posted as 1.505
 
vvcin auto
 
core 44x
core volts 1.250
 
that how it worked for me first time, 10h in intel extreme tuning utility for a night
 
maybe u need to increase a little vvcin? what was your default? mine 1.780, try set manually to 1.880 maybe 

thank you, i`m really happy with x44 and 1:1 ratio, don`t think i`ll need more.
even at default 4670k is great processor for gaming

1- your voltages are very acceptable well done.
 
2.  safe vCore 1.5V or lower
    
     safe cache voltage 1.45V or lower
 
3. cache speed does impact performance. your always best off if you can run at a 1:1 ratio and you will maximize your performance\watt but dont obsess over a 1:1 ratio. cpu frequency is still king

set ram clock manually and make ram voltage 1.55 it helped for my stability