There's sleep, and there's deep REM sleep.
I may sleep for a total of 4-6 hours at night, (rarely more.. tho' sometimes more, and sometimes even less), but much of that sleep time is spent tossing from discomfort/pain or inability to get relaxed, and when I toss, my spine, hips, and sometimes knees wreak havoc.
Add to that the fact that when the pre-sleep cannabis high wears off (different periods of time for different strains), my body comes out of that, and I'm awake, often with munchies. (Dried natural Turkish apricots and walnut halves are good ;^>) ).
I'm not what I would call a 'heavy smoker,' but rather a paced smoker of potent strains.
I remember some of my dreams, but if I don't relate them to someone else as soon as I wake up, then I'm more apt to forget them... which can be frustrating too. Especially when they were intense, disorienting, unnerving, etc. And some certainly have been.
As written earlier, typical bed-time, or back-to-bed formula is a few sizable potent tokes, and a potent single beverage. 8%+ beer, or tequila and juice, tequila with limne, or the whisky, maple syrup and low-fat milk concoction I wrote about earlier
What's more frustrating, however, is knowing I was 'asleep' sufficient hours that I -should- feel rested, but waking up fairly well exhausted none the less.
The penance we pay for having abused our bodies, souls, and the world around us, I guess.