Veronica, you just reminded me of something: years ago when I first started growing rosemary I would plant it in my garden and leave it and usually lose it during winter. One year I decided to plant it in the front garden that grows between my walkway and one of my front brick arches, which meant my house sheltered slightly on one side and the arches on the other. That was the year I realized with a little shelter from the weather, it could survive here. Those were the years before my zone jumped from 6b to 7.
In 2010, the year of the Ice Storm of the Century (!) when we were covered with ice and no utilities for 10 days, that little rosemary bush was buried in layers of ice and tree debris. I couldn't see it for awhile because it was frozen to the ground and I wouldn't let anybody move the limbs away from it until it thawed. That was its third year to grow and though it lived through the summer, it didn't survive till the next one.
So Anni, I've found that what you say is true, it's dry out there beside the brick arches unless I water it and I don't usually, and it's sheltered, but even so for me they only survive at the most about 5 years.
Interesting and strong plants; I do wish mine would get as big as yours and Sylvain's did, but so far, it isn't happening. The survival years and the size seem to be the only differences in mine and yours, though. Maybe I just need a sea breeze.