Do you mean stacking/packing? This is possible but you will likely be sacrificing the underside of the 2nd or 3rd layer of parts as they'll be printed atop supports rather than directly on the bed. Also this will use more material than just running back to back prints due to supports needing to be added to support the upper layers of prints.
The time savings is shown in the print preview when stacking 4 gears 3 times vs just running the original 4 gears 3 separate times.
"A bird does not sing because it has an answer. It sings because it has a song."