About every three days. I just don't want to wash it more than that, so I'm learning how to make it look decent in between washes.
3a/b, F, normal porosity

Wash with either Suave Tropical Coconut, As I Am, or CJ Daily Fix
Condition with STC or Yes to Blueberries and detangle with Denman, rinse very lightly (baptismal rinse)
Add LAL gel, either Sport or Wet Look, scrunch with flour sack towel, and plop
Diffuse 5 minutes, then air dry