Unless you have perfectly healthy, virgin hair (& there are very few people in this category), a regular deep conditioning treatment is a must.  Use a masque anywhere from twice/week (for dry, damaged hair) to once/every other week.  If your lengths are really damaged, I recommend applying a deep conditioning masque to wet hair, put a shower cap on & wear it to bed.  Rinse the following morning for luxuriously soft, shiny hair.  If you have oily roots, be sure to apply the masque only to the lengths of hair.   My favorite deep conditioning masque: