Imu is not immortal! - The slaves owned by celestial dragons are a major plot point

We all have read about how Imu has been alive since the void century in the one piece world and also we know that almost all of activities happening in op world has and has had some significance in the past.

Celestial Dragons own slaves and use them for their personal uses but somehow those slaves are getting used to extract life from them and transfer to Imu.

It solves the question- How will luffy beat Imu who is immortal? - By freeing the slaves which will lead to a stop in constant supply life to Imu.