From what I understand, the VQ C-VTC system itself is very reliable as long as oil is changed. The entire chain drive system is supposed to be quite robust on the VQ40, but occasionally you will hear of someone with a guide or tensioner problem.
The early (2005-2010ish) Frontiers and XTerras had secondary chain tensioner issues, but those were long fixed by 2015. I have read about these engines sometimes setting VVT codes simply because of old/dirty oil, but changing the oil resolves them.
My XTerra (same engine, 10 years older) had the secondary tensioner issue, I fixed it about a year ago and it's getting close to 175k now and hasn't missed a beat.