They will lay a lot of eggs if they have nests and it wears them out. Your females lifespans will reduce by about a third on average with year-round access to nests, or this has been my observation over the last nine years experimenting with both situations with my finch population.
They don't need nests and while they like them, they can make males aggressive toward each other and females to lay so many eggs they get sick, though this is less likely with a balanced diet.
