when do they expire? expiration date is useful to know since it will give an indication when they will be available again for batch 4.

I predict there will be a big drop in price for batch 5, the reason is simple for batch 4 there are a lot of coupons for the people that did not want the refund which reduces the need for price reduction beyond the 7.7% for drop hash rate, and another 9% for difficulty increase, but as expected they will sell out quickly, for batch 5  all the coupons will be gone, and further increases in difficulty will force them to drop the price further, and by then mostly everyone that wanted one will have at least one, once they start selling from stock is when prices will be the lowest, just like it happened with the S1, history repeats. currently the s3 is the best deal for the money that I am aware of.