So for us, the garden and animals included - I'd say as long as we can get some successful crops. We've got a greenhouse, a huge one, plus plenty of chickens to supply us for the winter months and fall and spring here are very mild, so greens are abundant, plus there's even the wild weeds/stuff...
Also not to mention, raw milk straight from a good Jersey or a rich-supplying Goat is WAAAY better than storebought milk.
I hated milk with a passion until I drank some from one of our goats. Sweetest, creamiest stuff ever.