We are all boiling frogs
James Fallows objects noisily to the ubiquitous metaphor of the frog that boils to death in a pot of water when the heat is turned up gradually; he calls for alternatives. Andrew Sullivan seconds. Many submissions have to do with smell or noise to which we grow acclimated, and some with gradually increasing one's capacity for pain or discomfort or with gradually deteriorating capacities.
None of these quite wash. What gives the boiling frog metaphor its bite (and it's a good metaphor - that's how it got to be a cliche) is that the frog ends up dead. Unfortunately, the best analogues may be the things that really kill us: clogging arteries, growing cancers. In fact the boiling water is mortality. Every year is a degree.