I agree with three years = tradition. But even if it had been only two years, I might have still given at least one or two people a heads up that it wasn't going to happen this year. Even if just to avoid the awkward conversation that, if not inevitable, was at least fairly likely to happen. And you know, just so no one was declining other invitations or holding off on finalizing their own plans or whatever, in anticipation of your invitiation.