Does long distance expire, and can it be refunded or transferred?

Long distance never expires. You use it until it's gone.

It can't be refunded, removed from the phone number it was added to, or transferred to another number, including another Talkit number you own.

Using a temporary Talkit number while your number is being ported? Use up any long distance on it before the port completes. It won't move to your ported number.