It is a good idea to fill the Compound but still have monsters ready to be housed so that when your yard is attacked and you lose monsters, new monsters will be ready to take their place and defend your yard. Suggested having 1 King Wormzer ready in each Incubator.
With effects from 20th June 2012, players who have bought D.A.V.E. Club subscription and wanting Inferno Monsters at the overworld may produce them from Hatchery instead to save the hassle of transferring. They still need Magma to be produced, however.