Brake Disc Caliper problems of the 2007 Infiniti G35

While driving I experience extreme vibrations, coming from the right side of the car traveling at or above 65 mph. Once I reduced the speed vibrations did not stop, but it was manageable. I had my tires balanced and rotated the next day, thinking that would fix it. But once again it started, my vehicle has new tires and I had the vehicle aligned. After driving the car a couple more days, the vibrations stop but days later it began again. I was fed up, so I took vehicle to my mechanic and found that the right rear caliper had gotten stuck and it would not return to its proper place after brakes were depress, thus making the car vibrate after driving above 65 mph. I had the calipers replaced, but now the left side it vibrating as well. The vehicle had no visible rust or problems, perhaps caliper is or are defectives after only 7 years on the road.