So would it be possible for a tavern to have a constant supply of beer all year long provided that they (or their brewer) had supplies of barley and hopps at the time?
It also seems like there would be a fairly large supply of marmite produced as well. I don't think they would let that by-product go to waste.
Yes it would. I read once that it is thought up to 40% of a harvest went to the making of beer in some places. So, that should be enough to last year around.