I don't think that any of us here any the slightest idea just how stressful these cabinet positions really are. Ashcroft's gallbladder removal was directly attributed to extreme levels of stress. The other positions given 9/11 aren't much different though his was probably one of the worst hit. Most of these people are just looking forward to being able to spend time with their families again after four years of being a ghost on the homefront for all intents and purposes. They are human just like all the rest of us and they have limits, most of which have been crossed at this point.
Also, cabinet shuffles almost always occur at re-election time. Fresh talent brings in people who aren't run down and worried about ailing family relationships, health issues, and so forth. As important as these positions are to each individual they mean nothing if they risk losing their families in the process. In many ways the cabinet positions are a much more stressful job than the presidency itself.
Re-election is the only "good" time for those to step down that know they need to. Any other time and it can be touch and go politically in so far as damage control is concerned unless an obvious reason is at hand.
Given the suspect nature of the problems on both the domestic issues and the foreign policy issues it would seem prudent on several levels to get some new cabinet members in place.
