1.) I don't have a spare $2,500 just lying around. Even if I did, that would only get me the camera body, and none of my current lenses work well with full-frame cameras.

2.) Even if I did have money burning a hole in my pocket, that money would be better spent on things like lights, light stands, gels, lens filters, and so on.

3.) I haven't reached the limits of what my current camera can do. I take some decent photos, but I'm still getting a feel for exposure, dynamic range, and so on. The limitation on my photos right now is me, not my D40.

4.) I just got two new lenses for my birthday, neither of which work with the D700. I really should spend more time with what I have before I move on to something new.

5.) A better camera won't make my pictures better. What makes a great photograph is composition, subject, and lighting, not gear.

I've been repeating this list to myself for the last several weeks. It's going to stick one of these days.