My screen timeout is 30 minutes. On some business calls, I generally use speaker headphones so I need at times to use the keypad. Even if I receive a call it starts to dim in about 20 seconds. Double tap and it brings back the brighter display. I may have a solution; On one of my calls, I put my thumb over the proximity sensor and that seemed to stop the dimming. I would prefer a different way to adjust this though.