We use these same QD's in the PW industry (link
). They seal perfect when new, but after they wear, they leak a little until pressure is applied. It's significant enough that we won't use them for vacuum lines. That said, we are pretty abusive to them, and store them compressed 24x7. Hence, we wear out seals about every 2-3 weeks. I can tell you they will stand up to 210* at 3000psi, especially if you use viton o-rings.
In a brewing environment, they would probably work leak free indefinitely as long as you didn't store them compressed.