I will change my oil at 7500 mile intervals with M1 (for warranty purposes only otherwise it would be once a year in the fall) because I don't daily drive in hot, dusty, cold, stop and go city driving, short distances, speed tests, etc. I'm just a guy who uses my Z for weekend cruising and the odd commute to work. I would agree with one of the other posters that changing oil at 3K miles is overkill unless you actually drive your Z daily in the aforementioned conditions.
Also, for those concerned about oil temps you may want to have a look here:
SwRI: Sequence IIIG test for gasoline engines, API SM, ILSAC GF-4
This standard for API certification was developed for lubricating newer engines such as our Z's that rev higher, run hotter and have decreased tolerances made possible by today's manufacturing technologies. I would hazard a guess that this is why our cars don't go into limp mode until 280 deg F is attained. The Nissan engineers are confident that below 280 deg they won't be having bearing failures leading to catastrophic failure of the engine. But if the engine is consistently operated in the 5-7.5K rpm range then that's a different matter and most likely considered as not normal use for warranty claims.