If I can use one product and gain 95% longer-lasting color, do I gain more than 95% if I use more than 1 product?

No. You gain the same color protection regardless.

No. You gain the same color protection regardless. Every product, whether using one or multiple products, gives you the same protection.  By using more than one product, however, you will gain the added benefits of the necessary nourishing vitamins, oils and conditioning ingredients that are depleted daily from color-treated hair and need to be replaced for healthy, shiny hair.