The maximum length of conduit between boxes is the circumference of the earth. More than that and you will have over 360º of bends in your run. But seriously, it's not restricted by distance, it is restricted to 360º degrees of bends between pull points. I have pulled wire through 700'runs of conduit using a Mightymouse.
#54852 - 08/10/0501:05 AMRe: Maximum distance between boxes?
The only other restirction, is the pulling force and sidewall pressure that will result when the conductors are pulled into the raceway. If this is a long pull with large conductors, then you need to do a pulling calculation to make sure that the conductors won't be dammage when pulled into the raceway. Don
#54854 - 08/13/0501:58 PMRe: Maximum distance between boxes?