How many prototypes do you need before you have a series made? Sometimes one copy is enough. Sometimes you want five, ten or more. The right number does not depend on a fixed rule, but on the question you still have about your product.
A focused trial saves work by examining the uncertainty that could affect a larger run.
Start with one clear doubt
Do you just want to know whether two parts fit together? Then one test model can tell a lot. If you want to know whether different people can assemble a kit without explanation, you need several sets and testers. And if a part must be able to withstand daily use, you also want to be able to put a strain on it without giving up your only prototype.
For prototyping with laser cutting, start with a specific test question. A trial then becomes a targeted step towards a better product, rather than a miniature production run.
Test with the material you really want to use
A model made of cheap cardboard is fine to view a shape, but it says little about a click connection in plywood. Thickness, stiffness and finish vary per material. Especially for parts that need to fit exactly, it is wise to try the most important connection in the final material.
This also played a role in Zappie's construction kit parts. There, poplar plywood was eventually replaced by birch plywood. In the case of Zappie you see why the choice of materials is more than just a choice for color or appearance.
When is the test passed?
Agree in advance on how you will rate the product. Does it fit without forcing? Does the engraving remain legible? Can anyone put it together at a logical pace? With such simple questions you prevent a test from ending in “it feels good”.
If the outcome is clear, save the approved file as a new version. From that moment on you have a reliable starting point a larger or recurring production run. Not convinced yet? Then only adjust the part where the doubt is and test again. That is usually smarter than immediately ordering a larger trial series.