If your overclocking and looking for stability generally any wheres from a couple hours to a full 24 is typical. So that said if your running stock clocks a couple hours is likely fine unless your having stablity issues then 6-12 hours would be better. If overclocking I would recommend at least 4 hours up to about 12 hours unless you have mission critical workload then a full 24hrs isn't a bad idea.
I'm overclocking at 4.8ghz right now with a core voltage of 1.210, just wanna make sure with 4.8ghz on a Kaby 7700k I'm not gonna damage it with hours of consistent testing
Keep an eye on your temps. Makes sure you stay below 80C, IMO some might argue less the 85C is ok. I prefer less the 75C in my own rigs for example. If your temps are good this is a great way to break in your thermal paste as well as test your CPU. Regardless if the OC/temps are good going for a full 24hrs should not be an issue. Just don't make it a daily thing is all Only stress test when making changes to your OC and you should be ok, generally speaking. Yes it is possible something may fry, a risk every OCer takes. You should be OK though as long as temps are low and voltages remain below 1.35.