Similar experience here... I am able to look at a computer or phone screen right up until I go to sleep. The time at which I get sleepy, and ready for bed, has to do more with my overall daily routine. I practice patterns of making myself go to bed at the same time. The screen time does not seem to make me stay awake. Also, if I am not sleepy when it is 'bed time', exercise after work is a sure fire way to get to sleep earlier.