Studs can never be 2-3 feet apart...it is against code and the building would not be able for living until the studs are as such. The 16" stud separation has been around basically since framing has been. The ONLY time you will find studs greater apart than 16" is in government framing. They separate theri studs 19 3/16" so that over the course of 10 feet than have saved 1 2x4, making it cheaper to build a government building.