so lets ask ourselves does Izanami last forever once its cast? Obvious answer is NO.
We can learn lots about izanami given its relationship to Izanagi which we know more about.
Izanagi(whether your an Uchiha or Not) there are limitations
1) The duration of the illusion casted on oneself varies from sharingan eye to eye. Orocihmaru via unnatural means helped Danzo extend the duration to about 60 seconds which according to Tobi(also an Izanagi user) is longer than usal.
2) The price for each cast is one eye loses its light and shuts permenatly.
Sasuke and Karin figured out how to deal with izanagi by knowing how long the illusion goes for and when it starts and ends. Danzo in the end got too nervous and didnt pay enough attendion to sasuke and to his sharingan eyes instead.
1) If izanagi has a duration based from one eye to another, would it be logical to say Izanami has aswell?
I think its safe to say ofcouse Izanami has a duration.
But what is the duration measured in?
Is it time like izanagi?
Number of loops the enemy can go through?
Is it both?
I'm thinking as long as the user has enough chakra to sustain the genjutsu will remain active. There is major chakra usage involved with Izanagi and Izanami is no different. Itachi is an edo tensei but this is a unqiue case.
So whats the punch line?
The major factor in how long this jutsu will last for is based on how many times the enemy can through the loops.
So if Izanagi's duration is based on the users abilty since its cast on yourself then Izanami's duration is based on the enemies abiliy as the genjutsu is cast on them.
2) Just like Izanagi, Izanami also takes light away from an eye per cast.
There you have it good summary of Izanagi and Izanami.
Intresting enought Izanami unlike genjutsu allows the target have a say of when the technique ends.
So do you think Kabuto can endur enough loops for the jutsu to end?