Once they are harmed in battle they are harmed. They are just a ninja tool. Like a kunai, if it breaks it breaks. You can mend it together again but it won't be Bibidy Booby Boo, where it is all fixed again.
For reference, with Kankuro's puppets they had to be fixed after Hiruko. They didn't form back together or else it would be an invincible jutsu, and like Itachi said, "Every jutsu has at least one flaw."