how far is boxers supposed retirement?

"At the beginning, when the laws of Animal Farm were first formulated, the retiring age had been fixed for horses and pigs at twelve, for cows at fourteen, for dogs at nine, for sheep at seven, and for hens and geese at five. Liberal old-age pensions had been agreed upon. As yet no animal had actually retired on pension, but of late the subject had been discussed more and more. Now that the small field beyond the orchard had been set

aside for barley, it was rumoured that a corner of the large pasture was to be fenced off and turned into a grazing-ground for superannuated animals. For a horse, it was said, the pension would be five pounds of corn a day and, in winter, fifteen pounds of hay, with a carrot or possibly an apple on public holidays. Boxer's twelfth birthday was due in the late summer of the following year."