"Print the label for the first package and then look for this "print additional labels to the same buyer" or something similar. It should do that for as long as you need. Alternately, go back to My eBay and click Print shipping Label."
Be careful when printing additional labels. You don't want to use multiple labels with the same tracking number. That might cause a complete breakdown of the U.S. postal system in the weeks following.
Hopefully you covered the cost of postage on each additional unit. I never sell larger items so I haven't run into this. I think I would set up separate listings with lot numbers assigned to differentiate them so I could print separate labels. I have done this in several cases where I have non-identical multiples of certain items that look the same on the outside.
