I have never had sleep problems. As I get older I seem to need slightly less perhaps. Usually I just go out like a light as soon as my head touches the pillow and don't wake until about five minutes before I need to. I cultivate good sleep because I enjoy my dreams and think about them a lot. My wife, on the other hand, has always had a shocking sleep discipline - goes to bed in the early hours of the morning, wakes up, eats, drinks, watches television, back to bed, up again, often sleeps during the day.
The amount I have to drink falls a long way short of causing hangovers. I drink coffee but it has never had any noticeable effect on my sleep. I suppose three or four cups a day is too little intake to cause bother.