golf007sd, I wish I could have kept my D700 and had a second body, but $4 grand had to come from somewhere for the D800e :( Your right though there is nothing like having two bodies especially for avoiding crap collecting on your sensor. When I finish my graduate studies I will have a D700 again as my second body. The D700 is still the best camera I have ever used even after nearly four months and nearly 20,000 captures on the D800e now..
Kanuck, given that you already have an amazing FX body, I would recommend considering a DX body as a backup. The added 1.5 crop factor really does come in handy, specially if you have good glass...which I know do. Moreover, it sure help keep the cost down, which as we all know, goes toward more Nikon kick-ass glass. :P