Really depends on the temps of your chip, your comfort level delidding, and what you actually plan to replace the paste with etc.
https://www.eteknix.com/intel-core-i7-7700k-kaby-lake-delidding-analysis-make-difference/4/
At stock, you can so (as per the link) a near 20'C swing under load, all else being equal - but YMMV.
Personally I'd say, if your OC is stable and a safe temperature - and you're happy with the performance; then there's no "need" to delid.
Also remember, if you do it on a new CPU, you're throwing that warranty out. Delidding will void a warranty.
The chances of a CPU failing within the warranty period (if it works to begin with) are slim..... but the benefit of the warranty is nice.
I'd only really suggest...