The acceptable maximum current for a connector depends on the thermal properties of materials used for contacts, connections, housings but mainly insulation.
It is a function of the heat developed in a connector operating and of course the temperature of the environment in which it is located. Preliminary tests determine a current-carrying capacity curve. During these tests, a common intensity is applied to the connector for 20 minutes, at the end of the 20 minutes the temperature rise is measured. Gradually the intensity is increased in increments of 20 minutes until we reach the maximum acceptable temperature by the fact of its various components. The current-carrying capacity curve thus defined then easily permits to validate a connector will safely operate at a given intensity and at a given ambient temperature. In all cases the sum of the ambient temperature and the temperature rise must not exceed the upper limit temperature of the materials constituting the connector.

The above calculation is valid to the extent that the intensity passed is identical in all contacts. For some applications a high intensity in one or more contacts is necessary while all other contacts of a connector will bear a small current. In this case, referring to the current-carrying capacity curve will lead us to choose a larger size of connector and contacts than is really needed. Only a test in real conditions could determine the relevance to retain a connector of a certain size. Practice warm-up tests for each case met would be costly and time consuming to implement. 

SOURIAU - SUNBANK Connection Technologies, through its calculation software developed over the years, knows how to calculate quickly and reliably what will be the maximum acceptable intensity for a given arrangement in a given connector.