Have to renew it once the first past expires.

For the 14 day pass, it expires 30 days after activation

For the 30 day pass, it expires 45 days after activation.

Hi ​@Jim Youngblut you can add a travel pass multiple times but they cannot be stacked or activated at the same time. 

You will be able to add the pass again once the first one expires, just be sure to add it after the expiration date, not before. If you add a second one while the first one is still active, it will just replace it.