If your chip is as good as you say it is, keep it at 5 GHz and 1.36V. That will be safe for quite a long time from now. I've worked with a dozen or so Haswell/DC chips and you don't want to run those puppies higher than 1.4V for a prolonged period. I had a 4770K degrade at 1.42V within months, your mileage may vary.
PS: Don't ever use Prime95 on Haswell/DC or Skylake chips. it draws way too much power and is completely unnecessary.