I run Mobil 1 5w30 in my 2007 Frontier. It has about 47,000 miles on it now. Runs fine on that and since I am really out of warranty, I go longer than the 3,750 miles for severe service that Nissan demands for warranty coverage. I go about 5000 or a bit more right now.
Two things to watch for on your Frontier.
1. The nylon timing chain tensioners wear out and have to be replaced. You'll hear a high pitched whine. If you don't replace them, the cain eats through them and hits metal and ....big bucks. Had mine done under warranty around 37,000 miles.
2. The transmission fluid cooler in the radiator can crack, letting coolant into the tarnny. Symptom of this is a bucking motion at steady speeds. Only real cure is to replace the entire auto transmission and the radiator, around $4000-5000. Nissan has exp\tended the warranty but I think you are past the extended warranty.