I feel my D50 has passed a bit of a milestone as I just went past 50,000 shutter actuations. I think the D50 was "tested to" 50,000 actuations, or something like that.
I've never had any problems with the camera, but it does make me wonder how much longer the camera will go, and that maybe I'm living on borrowed time with it. I do have a D300 as a "backup," but I still use my D50 a lot, and for most purposes I feel the results from the two cameras are indistinguishable. Even though the D50 is a few generations behind the state-of-the-art, it is still a fabulous camera!