What is the life span on Nissan frontier brake pads?

It really depends on how you drive, and under what conditions are where you are.

1. Do you stop and go in city driving where you always are hitting your breaks? Are you on dirt roads?

If so I would say from 50 to 60000 miles.

2. Do you drive on interstates or long drives on good highways distances?

Way over 10000 miles.

I drove 120+ miles a day to and from work, with 150,000miles on it and had almost 1/2 the pads left when I had to change them. The truck sat for almost a year as I had a stroke. 1 of the calipers stuck and wore 1 pad down to less than 10% left. I replaced the caliper and pads even though the ones on the other side were only showed about 50% wear. I also got over 100,000 miles on the tires. It is also very simple to install new pads on and cheep, unless you have let them go until you have metal to metal.