To maintain the desired color and avoid brassy tones, you should use toning products tailored for your blonde hair once or twice a week. However, it's essential to read the instructions on each specific product, as the frequency might vary. Toning shampoos, such as purple shampoos for blondes, can help neutralize the brassiness. When using a toning shampoo, make sure to distribute it evenly on your hair and leave it on for a few minutes before rinsing it out.