On that particular engine [QR25] I would do exactly what you are doing now, don't change a thing. Extending your interval will most likely increase your consumption a little bit which is exactly what you want to avoid.
Th QR25's failure mode [supposedly fixed in 2007] is that oil consumption causes the high mounted catalytic converter to degrade. Turbulence sucks particles of the converter back into the combustion chamber and scores the cylinders.
My brother-in-law had his old company car's [2010 Sentra Spec-V] engine replaced on warranty for excess oil consumption. Nissan asked that under no circumstances was the engine to be opened, just send it to them in a crate. The dealership used cruddy Nissan SL oil on way too long 3,000 or 6,000 mile intervals though, which probably contributed to the damage. [15w-40 or 20w-50 SL mineral that they rate for 1550 miles or sketchy Nissan 10w-50 synthetic]