This tool will help to make instances. Instances are references to existing objects, so they take almost zero memory (a memory-saving method of making duplicates of your voxel objects).

If you have some element that may be used multiple time a separate volume you may use it as instance. For example it may be brick or some mechanical detail. You may create mirrored instances, for example left and right arms.
Instances consume far less memory than duplicates. You can “Clone” an instance (Right Click menu) and “Import” new objects as instances. Negative volumes can also be instances.