How long is the enrolled card valid? Is it connected to the physical card?

The enrolled card is a digital version of your physical card, so it is valid until its expiration date.

When the physical card has expired, you will no longer be able to use it either in BT Pay. 

If your card has expired, the newly issued BT card will be displayed in your card list even if you have not yet received it physically.

You press the button „Add card” (located in the upper right corner of the screen when you open the app), and after adding your new card data, a confirmation SMS will be sent automatically to your phone number.

Enter in the app the sent code and that's it, you have the new card in BT Pay. 😃