Longevity moon cakes

Moon cakes are already on sale at the local Asian grocery shops two months before the Lantern Festival. The cakes seem to have perpetual shelf life. I imagine that it would take at least a month from the time of production in China or Hong Kong, importation into Australia, and finally arrival at the grocery shelf. Assuming they are still good for consumption a few weeks after the Lantern Festival, the moon cakes must have a shelf life of at least 4 months. Imagine the pastry and egg yolk being able to last that long; I could use some of the stuff they put in there to make my body last forever. Some foodstuff shouldn't really have expiry date - we will guarantee to expire before the foodstuff does.