You are Sorta Right. Nissan Emissions Warranty is 8 - 80 . 8 Years or 80,000 Miles. Witch covers front O2 sensors i believe but not rear O2 sensors. And of course Cat Converters
In any case there are 4 O2 sensors on your Vech , it can be easy to get confused which is witch and the Sensors aren't as easy as they use to be. My Recommendation as long as you know the engine code call you local Nissan dealer and inquire about the warranty on this Remind them Emissions is 8 year 80k Miles warranty. I would Start there, .. Gl