rears wear out faster on rears on almost all Infiniti cars, unless your doing heavy braking all the time,
also No they are probably not recommending them early . its probably time for pads, as i have personally seen them go bad anywhere between 16-38k also if your brakes are pulsating you have warped your rotors, which you will need to resurface (cut) them to make them stop,, some times u can shave the pad down and save it, but its recommended you replace them every time, the need for a resurface is so your pads have the proper mesh/ brake in with the pad I.E. clean surfaces ...
/to cut back/ avoid noise, properly lube all shims ( and use FACTORY shims and pads ) if you dont resurface the rotors and just pad slap the rotor it will cause more noise...... due to ROTORS glazing
A. traction control
b. braking habits
C. pad type ( material used )