In my "old" gardens I had a border of Santolina c. (grey). Most would make it through the winter if I cut back to about 6" after a good hard frost, and then buried them with mowed up oak leaves after freeze. It's the freeze/thaw/freeze /thaw that gets to them most.

I, too, love the plant and learned with trial and error that it's one herb that can take really heavy mulch. The mulch only came off when I thought the ground was getting too soggy in Spring and I was relatively sure that no more hard freeze would come. I also made sure that when it was planted, it was in a Z6 protected microclimate.

Martie