FWIW I qualified GM in December and presumably received four vouchers then. I haven't flown since and now have eight vouchers in my wallet. Four appear to be wine and four appear to be scotch or bourbon (I know that doesn't matter, but it might indicate when they were issued). All have an expiration date of 1/31/2020.
I'm not sure when I'll get a chance to use them based on what I have booked right now - I suspect tho I'll find a way before next January.
