Yes it's true the longer you soak your fibers in the mordanting baths the better the colors, especially with dyestuffs that are prone to fading or being difficult. Madder Root is one such difficult dye material, always wanting to go towards orange with strong hints of yellow.

Rinse your madder root first, I soak overnight and throw that water out, 0r use it for my indigo vat,yep you can do that too.

Then soak your madder root for 30 days for the best colors.