Is that IF you are running a GPU as well, or anytime? Because I run my 9600k at 100% on all 6 cores and have never had a problem in the about 7 months I've been Folding with it like this. Running it like this actually reduces my overall clock speed, which consumes less power and creates less heat, but WUs take only about 2/3 the time compared to running at medium, so cost per WU is cheaper and when my system needs CPU cycles, it gets them easily (talking basic web browsing, mail, watching videos etc, not actual CPU intensive stuff).
Started running the BOINC client to run Rossetta@Home while waiting on WUs from the F@H server and it's not that nice, it ramps my cores all up to max boost, normally 4.3Ghz and uses about 15-20W more power than F@H. I even tried running them both at the same time and still haven't had any system issues or instability (clocks drop to about 4-4.1Ghz) and I'm in the Caribbean with avg room temp of 26C> and only a CoolerMaster Hyper 212 cooler with 2x120mm fans, 3 120mm intake fans and 1 120mm exhaust fan at the top of my CoolerMaster NR600 case and max temps with Rossetta of about 77C.