I've been watching these Starbucks threads with interest for a bit now and I'm considering trying this out...
When is the risk of these going "bad"? Like when you are at the register conducting a transaction (and then you have to come up with some kind of alternate payment method), or you see it in your account beforehand?
Someone in these pages mentioned having more than one card on an account... when one card gets taken to $0, the rest don't get $0'ed out too?
They can be closed any time any place. Usually if you "refresh" your card balance in the sbx app just before you purchase and it doesn't say "card closed" you'll be OK. Only the "bad" card gets zeroed but if you transfer even a penny from the "bad" card to a "good" card they are now connected and they both usually go down so never transfer balances to a "good" card (I lost my "Gold" card with over $300 on it that way a year or so ago after I transferred a small balance from an eBay purchased card I paid 90% for to it and learned my lesson). I spent an hour on the phone with them and the best I could get from them was "only buy cards from Starbucks." When is the risk of these going "bad"? Like when you are at the register conducting a transaction (and then you have to come up with some kind of alternate payment method), or you see it in your account beforehand?
Someone in these pages mentioned having more than one card on an account... when one card gets taken to $0, the rest don't get $0'ed out too?
. 1 gift = 20$. buy all = 35$ 
