Projection objectives, related systems and components, and methods are disclosed. The methods include providing a projection objective of a lithography projection exposure apparatus, where the projection objective includes a plurality of optical elements between an object plane of the projection objective and an image plane of the projection objective, and the plurality of optical elements includes a first optical element having a refractive power and being disposed in the projection objective at a first location. The methods also include removing the first optical element from the projection objective, and inserting a first spare optical element into the projection objective at the first location, where the removing and inserting steps are performed at a location of use of the lithography projection exposure apparatus in a lithography process.