A go no go check point should be used on every takeoff as low engine power, dragging brakes or other factors may retard the aircraft acceleration sufficiently to affect flight safety. I also teach the 2/3 at 1/3 as a general rule of thumb with the understanding that it may need to be modified for short fields
It is also important to note that the aircraft has to keep accelerating. I remember one takeoff on a muddy grass where I made the 2/3 speed in the first third of the runway but the aircraft absolutely refused to accelerate any further after that.