Okay we all know that Transplanted eyes are activated forever. I will use Kakashi and Nagato as an example.
Okay now here I show Sasukes transplanted eyes.
Now I show you Sasuke's eyes reverting back to normal. (no sharingan)
http://www.narutobase.net/manga/Naruto/590/4 (middle pannel and Bottom left panel)
Alright if Sasukes eyes can revert back to normal, then why can't Nagato and Kakashi revert there transplanted eyes back to normal then?
Obvious plot-hole. -_-