I'm working on a design that's to be printed. The size of the item is 1/3 of a standard letter page. I would like to be able to work on it in Illustrator only once without the copy and paste at the end. It's very tedious to make any kind of change.
Moreover, the printed result has to be multisided so ideally I would like to use two artboards (one front, one back).
Is this something that is possible to do in Illustrator: print one artboard several times on a page and multisided?
With this in mind, if you expect the duplex (2-sided) prints to line up to one another using an end user/home/office printer, you're going to be terribly disappointed.
Rereading your question, it sounds like you might benefit greatly from Symbols and using 3 instances of the same Symbol. With this, you only need to edit the symbol to see all instances of that symbol update - 1 edit, multiple copies basically.
You can also create 1 master .ai file. Save it. Then open another .ai file and place the master .ai file in the second file as a link. Edit the original, then open the second and the links should update. (InDesign is a bit better for this but works very similar)