Been through a lot of pain, "blood, sweat & tears", R&D, Trial & Error with my VQ35DE motor.
To save most of you guys time, I'll share what I've done and noticed from inspecting the VQ.
#1: Piston rings - seems to be the most probable and annoying cause, since the OEM rinigs have a light expander behind the oil scraper ring. For some reason Nissan changed them to these in '05. I ended up just buying a low mileage motor and building it ground up. (CP pistons, rings, Carrillo H-beam rods, pins, ACL bearings, ARP main and head studs/bolts, Cosworth baffle, IP billet girdle, etc.. Going TT)
#2: PCV valve - as said, it's best to have a catch can or breather setup in pcv valve port to regulate and remove fumes from the engine crankcase, and to alleviate crankcase pressure which could cause oil leaks or seal damage. ()
#3: Oil pump - most build shops all recommend switching to atleast the Rev-Up oil pump to keep oil pressure up and able to handle high rpm (7k)
#4: Head gasket - not often does a headgasket fail on these motors, but Nissan's new design with the VQ35HR's head gasket, helps cool the backside of the motor evenly. A small modification (grind 11mm deeper in block for water passage) is needed. I also recommend the Pathfinder Cooling Kit. Best installed with motor out. ( )
#5: Get a tune - keeping AF/R in check even after installing a few bolt-ons will really help the motor from running rich thus burning tons of oil
#6: Spark plug seals - I didn't have to change these, but have noticed a few owners that have had oil seep into their spark plugs. A good sign is when you're changing them, you'll see oil on the back sides of the spark plug. You can buy a whole valve cover gasket kit from here:
Add longevity to your motor: If you ever decide to rebuild your motor, I recommend getting WPC Treatment - wpctreatment.com - they have the technology to harden important parts of your engine, bearings, and other moving parts while also decreasing friction with their surface treatment. A lot of good results are coming out of this treatment...check out this live test:
To all the other techies or guys/girls with more experiences to add, please do.