Whats the maxium extent Goku has ever extended the power pole in the series? He uses it a lot in the series to do various lengths but do we know a maximum length, or the farthest hes ever extended it?
I think the farthest the stick has extended in DragonBall is the distance between the Earth and the Moon.
In DragonBall chapter 17, Goku fights a gang of rabbits whose Boss can transform people into carrots. Once they are defeated, he decides to take them far away, very far... directly to the moon.
So : 384.400Km or 238,855 miles approximatively (if the distance Earth-moon is the same in Dragon Ball than in the real world)
Goku of dragonball was inspired from The Monkey King from 16th century Chinese classical novel The Journey to the West.
The staff first appears in the third chapter when the Monkey King, Sun Wukong, goes to the underwater kingdom of Ao Guang, the Dragon King of the East Sea, looking for a magic weapon to match his strength and skill.
Upon Sun Wukong's approach, the staff glows to signify it has found its true master.
The staff is initially described as a pillar of black iron twenty feet in height and the width of a barrel.
It is only when Monkey lifts it and suggests that a smaller size would be more manageable that the staff complies with his wishes and shrinks. The inscription on the staff indicates that it follows the commands of its owner, shrinking or growing to their whim, make copies of itself.
Since it is magical and can grow and shrink according the command of its owner, I assume it can reach any length that its owner wishes.