In any given condition, there is a "best" size and age to which timber should be allowed to grow. These sizes and ages can be very different depending on the desired harvest scheme used and the final timber product to be produced. What is important to know is that a premature cutting be avoided before trees reach their optimum value or, on the other hand, that trees in a stand do not grow beyond their optimum size and continued vigor. Over mature stands can result in defective tree deterioration, timber handling and milling problems. There is also a time in maturing stands when a decreasing growth rate (of return) hurts the owner's investment return.
An optimum timber rotation is often based on and determined by precise calculated criteria using the latest developments in forest statistics and the proper equipment. These criteria include measuring a stand's mean diameter and height(stand size), determining the stand age in years, coring and measuring tree rings to determine the climax of mean annual increment and monitoring all these data for the onset of negative physical deterioration or when growth rates drop.