Is there a tool inside or outside of Adobe Illustrator which packs custom shapes inside an (say) A4 page?
This would be an optimization for printing the same element multiple times on the same page.
This example involves rotation, but it’d be ok without too.
In the restricted case where a rectangular array would suffice, you might speed things up using Effects > Distort and Transform > Transform. If you use Copies and adjust only the Horizontal move, you can quickly create a row that fits the sheet. Repeat the effect on the vertical to fill the grid, then Expand Appearance to create discreet objects. The advantage, apart from possibly saving some time, is that everything will be evenly spaced for cut and trim.
For a triangular shape, two objects, one inverted to minimize the total amount of space, can be replicated in the same way.
You might find the Pattern feature useful in this situation, since it offers a variety of different overlap and repeat patterns. The same “Expand Appearance” trick freezes the layout.