Hi @suzunosuke.miyahara  
Thanks for reaching out to us 
There is not a way to check expiration date of refresh tokens. 
Refresh tokens are valid for 90 days
  
  
    I have a multitenancy application that is set up with an OAuth Zoom App integration. OAuth integration goes well, and generally speaking the refresh token is changed out for a new access + refresh token. There are some scenarios where the refresh token may not be used/changed for more than 90 days and I see that that is the new expiration time on those (compared to the previous 15 years). 
Is my only option for getting new tokens, to re-authenticate the application? 
Furthermore, I was trying to…