I don't think there is any expiration date and you can set any. But there is a feature request to have an expiration time on pin settings:

https://ideas.ringcentral.com/ideas/CUSTCOM-I-3450

Please vote the idea if you want the same

@Vishal Dubey Anirban is correct - there is no expiration. The idea he shared is specifically about forcing PINs and passwords to be updated.
If that is what you were hoping to explore, I would recommend using the link he provided and share your use case and any additional details in the comments.

Let me know if you have any further questions or we can help further.