As well as the G we have a 15 year old Nissan Quest with a V6 VQ 3.0 engine. I changed the oil every 5,000klm's ( 3,500 m ) We still drive it daily, it burns the same amount of oil it did when we bought it and it has 420,000klm's on it. Thats 240,000miles if your on the old system.
This Quest has also been a tow vehicle for ten years towing a pop up for 7 years and a 4,500lb Airstream TT for 3 years. The transmission has been problem free and still works fine. These drive trains are bullet proof. I have high expectations from the G.
Pic of Quest and Airstream...
http://smg.photobucket.com/alb...4.jpg