That's impossible to answer! It depends on CPU usage, length of up time, environment conditions (heat, filth, etc.), other BIOS settings that support the vCore, the rest of the system, etc.
66.8C is max recommended operating temps as per Intel. Time above that temp will matter too. Since Intel recommends a max vcore of 1.4v, you should be within the safe limit unless it peaks above that. Personally, I would not run it continually at that range. How high can you get the clock speed up to w/o raising the vcore?