Do a search in the forum for "everlasting" to see who else grows them and has posted something about theirs.

Everlasting is a commercial term for the hydrangeas developed by PlantsNouveau in Europe and they tend to be compact and useful for those who like to get flower cuttings from hydrangeas with pretty flowers. Not much of a claim to fame to me but oh, well.

They are similar to the ES Series in that they are remontant and bloom on either old or new wood. ES sometimes claims in some places that theirs are hardy to z4 but that applies to the roots. The one Everlasting Hydrangea that I saw locally had a z5 rating years ago; I do not know if they have changed that. But I would also assume that means the roots are hardy to z5.

I have two everlasting revolution hydrangeas. They are more compact (about 3' x 3' for me) and more sun tolerant (the leaves are thicker and more waxy) than the endless summer original. And while the bloom color is not as vivid, the blooms last longer. I personally don't really care for the color changing blooms, and I can't say that they are any more winter hardy than other macs, but they give me nice blooms without winter protection.