Add a Step and Repeat Feature
There are several custom script solution for this, such as:
Which means the demand is here.
Kevin Prutzman commented
This is already in Illustrator.
Shift+Cmd+M will give you the Transform tool. Then you just type in the distance you want to step. (horizontally and/or vertically)
Though it would be nice if you could enter in a field how many times you want it to step. :)