Wow this is an old thread!
I remember my first NSX oil change I did in Cali and they charged me $20 labor as it was their standard oil change fee which included filter, washer and displosal fee. I supplied the oil.
Now I do it myself but as Stu said, I send my oil for lab analysis every time I change my oil just so I know what is going on and the results always indicate less than 40% wear and lots of additives left.
I've pushed my daily driver to almost 10k and the Mobil 1 showed 85% wear and the additives were significantly depleted. Probably left it too long, but changing my daily driver at 6k showed the same results as the NSX so the sweet spot is probably around 8k.
Go to Costco and get the Castol Synthetic for $35 for 6 litres. Castrol has 30-40% more additives than the comparable Mobil 1 so it will likely last longer. Then again, if you do your own oil changes and would rather change it more often since it only hurts your pocketbook, save the Castrol for your daily driver and get Mobil1 at CT on sale for the NSX...
Lab analysis costs me $25 a pop so that is about $60 total with filter when I do it myself.