So is the seconf and the third ... 4th perhaps but I haven't gone there in a A/C.
Tip: There is nothing to stop one from going back and requesting more after using your first voucher(s).
I done this many times; plenty of others have posted here and on FlyerTalk about this as well.
UA have ditched their vouchers and offer basic alcoholic beverages (AKA "Well Drinks") on a complimentary basis. One needs to pay for 'premium' beverages. (More on that here:
RCC/PC annoucement - free WiFi and snacks, alcoholic and non-alcoholic drinks - FlyerTalk Forums)
AA also are now providing basic alcoholic beverages on a complimentary basis; however, they are still providing vouchers for 'premium' drinks to those who entitled to them on the same basis (e.g. Non AA oneworld emerald/sapphire, AA EXP/Platinum travelling "to outside North America+MEX", QP members).