The instructions I followed had the key generated in Adobe Experience Manager:
Integration with Adobe Target using Adobe I/O | Adobe Experience Manager
When viewing the certificate in console.adobe.io, the expiration shows 2031. It looks like the steps are a little different from what you provided so I will work through this document. Thank you!
Update: I am unable to link the key generated from console.adobe.io back to AEM. Our AEM instance is not currently configurated in IMS. From what I can tell, I am only able to create a new key or use an existing one that was created in AEM, but not upload one created from console.adobe.io. Is there a web console configuration that can be edited for the default expiration?