how many miles can i expect to get out of a nissan maxima s 2015 during its lifetime?

As much as you take care of it. I've had vehicles get 500k miles out of a gas engine.

I have a friend who had a 1995 Maxima that rolled over 400k with only normal maintenance he did himself. Oil changes (every 3000 miles), spark plugs and wires, manual transmission gear oil changes, and the like. Still ran pretty good for something with so many miles. It's all about how you take care of the car. Abusing it all the time and not doing normal maintenance will shorten the lifespan of it. This is why there's many cars out there breaking the 200k range. It's not the make or model, it's how the owner has taken care of them. The "average" lifespan of a car in mileage is about 150k the last time I researched anything on the subject. Pretty sure that stat also consisted of vehicles that were totalled dropping the average. My father in law has a 2004 Toyota Tundra that's hit 300k miles and still runs great. Normal maintenance, including swapping the timing belt every 100k (toyota's specification), and taking care of it has kept it on the road for many miles. He expects to get at least another 200k out of it as it uses no oil, and has VERY good compression for it's age.

My 03 maxima has 270k on it and still runs great. maintenance is key.