If you prevent the air from passing through the pores in the shell, a long time - maybe over a year.
This may be done by greasing them with a film of non-smelly petroleum grease, bees wax, or by immersion in a sodium silicate solution. (waterglass)
up to 7 eggs at once
An emu lays between six and eleven eggs once a year.
it lays about 10,000 eggs at once
before it dies it lays thousands of eggs
A female leopard gecko usually lays eggs once a month
After a butterfly lays eggs, it typically does not live very long. The lifespan of an adult butterfly is relatively short, usually only a few weeks, as its main purpose is to reproduce. Once the eggs are laid, the butterfly's life cycle is complete and its role in the continuation of the species is fulfilled.
A Puffin usually lays five eggs at once
The female platypus lays 3 or 4 eggs once a year. The Male does not.
Platypuses breed just once a year, laying one to three eggs at a time. The eggs are soft-shelled and leathery.
African grey parrot eggs typically take about 28 to 30 days to hatch. The incubation period begins once the female lays the last egg, as she will start sitting on them to provide warmth. Both parents may share the responsibility of incubating the eggs and caring for the chicks once they hatch.
The echidna usually lays just a single egg at a time.
Snowy owls are birds not mammals so they lay eggs they do are not a species which can become pregnant. Once the owl lays her eggs it takes around 5 weeks for them to hatch.