Clarification on access token expiration

Hi sorry to raise an old thread,

I am wondering what the system offers when I have multiple cores I currently have one and have two more on order. The id and authorisation code are stored in a mySql database. These are accessed by a front end application written with Access. My hope is to have several hundred of the cores in my database controlling machines out in the field. May I ask you to explain to me how I can chose which core to renew the token on, all of the cores will be registered to one account. Ideally I would like to automate renewing codes and store the results in my database any thoughts on that would be much appreciated too.

Best regards,
Clive