I have to be mentally exhausted to fall asleep within minutes or even an hour. Doesn't matter how much physical work or exercise I've done or how tired my body is, my brain doesn't shut off until I've exhausted it. It's left me with many sleepless nights - or napping for three hours and going another extended amount of time without.
Never bothered my ability to function though... except made me jittery and chatty.
It really depends. When I was young I always had a hard time falling asleep, it would take me hours. When I started working a "9-5" type job I went to bed at the same time every night b/c I had to get up early. After the first few weeks I found that I was falling asleep within 5 minutes of laying down.
Now that I don't have such a strict schedule, I'm finding that it's taking me a longer time to fall asleep. About 30 min to an hour.
Hey, the brain damage is not my fault and it isn't slowing me down much. I cut out caffeine mostly, so that helps some. I am going to try a new sleep med soon, I hope.
What can I say? You just make the best life that you can with the hand you're dealt. If life were a game of Texas Hold Em, I wasn't dealt the deuce-seven off suit, but some days it feels like it's close. I deal anyway.