Title says it all (while also assuming there was one). No right answer, tho no doubt a couple wrong ones, but what stretch do you consider the standard for peak HHN?
My own proposal is 2005 - 2011. The fact 2005 is still actively being discussed today shows what a game-changer it really was. Followed by very good to great years* where even the failures were at least interesting, until the event hit the wall of 2012 and TWD. (I'd argue 2019 - 2023 have been a Silver Age that hopefully continues.)
* - HHN19 probably the outlier here, but at least 3 highly regarded houses, a solid B&T show, introduction of the Usher, and an attempt to do something different with the zones.