If someone is actually expecting to get 2 years out of their Sandy using it 24/7 I'd say stay well below 1.40v preferably below 1.35v should be very safe, most 2500Ks will run 4500mhz in the 1.300v ~ 1.330v range.
Presently 4500mhz will do whatever you need it to do, so there's really not much reason to clock it any higher once you satisfy the curiosity of reaching the higher clocks.
Of course it also depends on how hot your CPU is running 24/7 at 4500mhz with the voltage it takes to achieve stability, the cooler the better so that's also an important factor.
It also depends on whether you're running stress tests all the time as some out here seem to think that's a daily duty, stress tests are to reach a stability point then stop running them as they are shortening the life of your CPU.
If CPUs had a MTBF rating in hours then what I just wrote would be easier to understand, if say for instance a cooling fan is rated MTBF 50,000hrs @ 12v but you decide to run yours at 14v, do you think the fan will still last 50,000hrs.
Well you could actually say that you have 26,280 hours before your warranty runs
out, but some on auto voltage are running higher voltages than those of us manually overclocking, hmmm, could that be a problem.
Curious that your M/B warranty runs out before your CPU warranty does and your M/B is what's actually regulating that extra auto voltage,and cooking up your CPU!
Well you did ask for opinions.
Everything on this planet has an end, the key is how fast will you reach it?
Are voltages left on auto good or bad there's something to argue about, IMO when voltages are set manually they're fixed at a certain level, voltages on auto fluctuate sometimes going to extreme levels to keep the computer from crashing and catch up to what's going on.
It may seem the safest route and easiest to accept and be pleased with but sudden electrical surges are not good no matter how low the voltages are, especially when some of their peaks are way past what you'd like to safely use daily.
Some motherboards run auto voltages way higher than needed, but they never designed the things to run forever if they did you wouldn't need to buy another, and they'd go out of business.