What is the effect of giving multiple of the same Resource?

[SirReptile]

If I give multiple of the same resource (dust, neutronium, etc) to a race at one time, does the effect stack? Does it last longer?

For example, Neutronium "gives a race a 50% bonus to armor." If I sell two to a race, does the second add more armor bonus or does it add to the time that the armor bonus lasts? Or both?

[Shadow]

The more you give them the longer the effect will last.

[SirReptile]

Thank you for this answer! How long does the effect last for each given resource item?

[Shadow]

It depends on their level and how many planets they have (if I remember correctly).