Apparently, it takes two hours to achieve R.E.M. sleep (rapid eye movement), the deep sleeping state which is actually beneficial, and in which dreams occur. This may explain why I never sleep through the night, but wake up at periodic intervals, and why I rarely dream nowadays.
I was so tempted to leave it at "Apparently, it takes two hours to achieve R.E.M." which is probably also true, and would explain why they suck.