I prefer to replace a backflow that's been frozen. I don't have a lot of faith that the brass survives the experience without any warping. I don't know whether the Febcos have any problems passing testing, if they've been repaired after a freeze-up. Actual testing requirements haven't yet been legislated by the states around my neck of the woods (NYC) ~ I have a Watts TK-9 at the ready, but it's all dressed up and nowhere to go.
I do tend to look at a PVB in terms of its primary function of a 24/7 vacuum breaker. I don't use the Febco 765, because of the plastic bonnet, which makes it too fragile. A few older designs have brass bonnets, and I've chosen them. If I was looking at a PVB in terms of its pass/fail performance in check valve testing, a different picture might emerge.
