while it's not the preferred method to achieve a long life for your CPU, i had a similiar situation with my i7-4790. I had built my first rig on an Asus board and was using Asus's AI Suite III to watch temps - it seemed to always float up to 67C and never go above. I was rendering a lot of video files, some 1+ hour jobs to 3+ hour jobs and had used it for 3 months or so doing 5-10 jobs a week. That was almost 4 years ago,
I downloaded RealTemp and it was showing, while rendering, temps floating up to 100C, then dropping to 97 or 98C, and the climbing back to 100C, and it was a never ending cycle. Downloaded a few other temp monitoring utilities and they were showing the same.
like you i was on the intel junk stock cooler. Upgraded my cooler to correct the temp situation I started using Intel's XTU, and in their benchmark utility, once you've run a test it offers you the opportunity to upload your score to HWBOT on the internet to compare to other users - and you can select only users with your motherboad and cpu.
Every time i run onem i score in the top 5% so i doubt my cpu was damaged,
Intel has thermal limit safeties built into their CPUs, so that when it approaches one of those limits, it throttles the load back to keep the heat in check - that was why mine was dropping back at 100C, falling to 97 and then climbinb back
there's an interesting tutorial on CPU temps limits here on Tom's you might want to review - but the short of it is you want to try to stay below 85C
http://www.tomshardware.com/forum/id-1800828/intel-temperature-guide.html
Oh you might google for and download RealTempGT - it minimizes to a small widget sized window but has a helluva alarm built in - you set whatever temp you want for the alarm, and i promise it will wake the dead when it hits that temp for more than 1 second or so - if you do run it, run it with HWiNfo to confirm temps it's reporting