Page 7-5 in my 1998 manual talks about the Engine Oil Life Monitor. It says you should change the oil between 3000-10,000 miles, but never beyond 10,000 miles. It also tells you that the monitor will tell you when you need to change your oil. But, it will not detect dust in the oil, so if you live/drive in an area where there is a lot of dust, you'd want to change more frequently than the monitor says (every 3000 miles in this case).
The service records from the previous owner of my Vette indicate that he usually went 6000-8000 miles between oil changes, and I have noticed no problems with the engine or oil system as a result of this. Those numbers are pretty inline with what I'm seeing, too. I've driven the vehicle about 3700 miles since I got it (when the oil was changed), and my EOLM says I'm at around 45% life remaining. I plan to have the oil changed when it reaches about 10-15%.
I personally feel that, except in extreme conditions (the dusty area, for example), the every-3000-mile-oil-change recommendation is a bit like the directions on the shampoo bottle: "Lather. Rinse. Repeat." The more rapid replacement cycle is fine and dandy for those providing the products and services, but a little bit overkill for what the consumer actually needs.
