Tool Length to Diameter Ratio
Ideally the cutting length should stay under a 3 to 1 ratio. Cutting length divided by Tool diameter. For example 1/2 tool should have a cutting length out of the collet of no more than 1 1/2 inches.
Advantages are as follows :
Less vibration = better surface finish
Less spindle bearing wear = longer spindle life
Better too life = increased cost savings
Less tool deflection = see 1 - 3