Invisible expiration date? That's the weirdest rumor I've ever heard I highly doubt it's true. The heart should be permanent (it was in KMS).
It just follows you around and you can command it to make faces by saying certain things (look up an android guide)
1. You are getting trolled
2. It's special cuz it's FREE. Nexon specializes in FREE as you can see. FREE to play all Nexon games! Cuz you can and its Free!
3. You will receive beryl heart in a later hot time to use with this roid and that heart will be permanent as well.