It will last a long time and give some yield after the dust is used up. I am sure it has been contributing to what we grow. Sometimes the gravel pits have mesh screens and can measure the exact fineness of the gravel. You will have the finer material immediately available to the soil and the rest will break down over time. The gravel pit may have machinery to crush the rock finer and may crush it for you.
Soil erosion is an effect of the shortage of minerals available to support the soil organisms.
When that is done, the soil microorganisms begin to multiply and it is they who prevent soil erosion by granulating the soil and holding it against both wind and rain.