Yeah, it sucks. You get 3 of them but they are each good for 1 item in 1 factory and it expires in 2 hours. I did not try to see if I could set another item up within those 2 hours after my 1 item was made. Experimentation time!
EDIT: Just experimented with bread.
Activated the coupon.
Filled the boxes in the bakery. Two started.
Let them run until done, both started again.
Skipped both when they got under 2 minutes, both started again.
Conclusion: it will be helpful if you need many items made in 1 factory and their completion time is short and you have enough ingredients to keep filling boxes.
EDIT 2: Bread was just ending so I queued up bagels and both started making bagels, so you can change the item inside the factory within the 2 hour limit but not the factory.
It does not matter what the item is, it will pick up the next box when it finishes 1.
Im interested to see what will happen if it is working on a box when time runs out, so I have scheduled a regular pizza after a seafood pizza. It will be 6 minutes into the regular pizza when time is up.
EDIT 3: The Extra Hands keeps going and finishes your item after time runs out on the coupon!