I used to do this. I had the same suspicion. About two months ago, in an effort to improve my sleep quality, I banned the iPad (and all other devices, except a first generation books-only non-backlit Kindle) from the bed when sleeping. My sleep is indeed better, in part because I no longer spent "just a few more minutes" randomly browsing before going to bed, in part because if I wake up early or in the middle of the night, I can't just reach for a device and start checking email.