Hi. The first camera I bought was a Nikkormat Ftn in the summer of 1972. With a 50/1.4 lens, it cost $315.12. (Cash from my summer job as a counterman at The Pep Boys).
Since then, pairs of F2AS and F3As.
Then (late to the party as ususal), in 2005 I bought a pair of D2x's. Wow, they were great cameras. I still have 'em -- and I still use 'em. But they're not good for everything. I have no problem with relatively slow-moving things at ASA 400 and below.
I bought a D4 in August, and I was amazed how good the SOTA camera had gotten. I have no problem running exposures as 12,600, using whatever light is in the venues. > >But - why, I mean really - WHY move up to a D3 or D4 with >those huge sensors and massive file sizes unless you have a >very specific reason?
For me, it's faster autofocus in low-light, and the ability to jettison my SB-800s if I don't really need the extra light. I don't make gigantic prints, and as much as possible, I print full-frame. (I don't crop much outside the camera.)
I typically shoot single frames, one after the other. I'll make 100 - 400 shots during any sort of ball game. I've used CL and CH modes only to make sure they work. That's just a residue of how I learned to work. I wait for that decisive moment, and my reactions are good enough to usually get it on film.
I make about the same number of exposures with digital as I did with film. I just don't have to count backwards as well.
I'm presuming professionals whose work demands they shoot high numbers of exposures will wear out a pro Nikon in fewer years than I will. (The D4's 400,000 shutter clicks will take me a while.) That maybe why they replace so often.
Use the tool that makes you happy, and gets you repeat clients. I still shoot a lot of 4 x 5 sessions. Scan those negatives, and you're talking some B_I_G files!