IMO a lot of the "K/unlocked" CPUs that Intel has been releasing in recent years are essentially expected to be overclocked by the manufacturers. Same with GPUs - they all release software programs in order to facilitate overclocking, and nearly every bios on any "gaming" or "enthusiast" type of motherboard has all kinds of overclocking options, and many of them have automatic or "AI" one click options to "safely" overclock your CPU to a reasonable level. Even their advertising, and testing protocols often focus on overclockability.
I agree with the above, you may take a few years, and only possibly, off of a CPU if you properly cool it and don't go crazy with the voltage and keep the heat monitored and in check, but in the grand scheme of things you'll likely have upgraded twice by the time any longevity forfeiture could become an issue.
That 3570k CPU was the overclocker of its day a few years back, very, very popular chip. Lots of em out there similar to it available now too. The new Skylake stuff by all accounts is clocking up pretty well. Our oldest system, a locked x79 3820 overclocked to 4.5 GHZ for over 3 years now, and it's only been powered off for maybe 2 hours total in that time, just to plunk in some video upgrades a couple of times, and that's on a 60$ Noctua air cooler too.
It certainly isn't necessary, especially with the power you can buy with not a lot of $ these days, but if you want that extra 10 or 15% (in terms of real world gaming performance increase), you are unlikely to harm anything if you educate yourself, or ask for help, or perhaps do both, before you try it.
Anyone remember the old Celeron 300a? Back when the P2 450 was "the" heavy hitter, along came this little wonder chip, the Celeron 300a, of which nearly all of them could have the snot overclocked out of them right up to 450mhz, at 1/2 the price or even less than the flagship chip. Back in the old Rainbow 6 and Warbirds 2.xx days for me, and I bought one as our 2nd gaming PC, and wished I hadn't spent all that extra $ on the P2 450 first, the Celery worked so well. I think it was probably the first commonly overclocked CPU in the PC gaming world 16+ years ago now.