What is the exact purpose of checking tool length? Is it really necessary to check the tool length three times before a run? This seems like needless time spent and wear on the machine. It appears necessary to chuck a bit and check length just to jog a dial indicator across the surface.
[Edit] D’oh! I guess measuring the tool length obviates re-zeroing after a too change.
As a precaution, the machine remeasures to verify the tool length any time it has not been in control of the machine so as to preclude the possibility of a user having changed the endmill.