Hi Jason,
Buddy Passes (S4) are paid for with a credit card at the time of booking, which answers your next question, yes you need to declare where you are going. Not sure about the expiration.. maybe one year from date of issue. If you do not use them for some reason, they are 100% refundable.

Vacation Passes (S2) are good for a travel day. Once you list as an S2 that is your priority for all flights that day.