Oh & I've had weed that straight knocked me out for 3 days, but typically it takes only a few minutes before peak effect and should last 1-3hrs. Coming down has the opposite effect on me as you described, makes me straight retarded and sleepy. Then again caffeine and certain other chemicals are also backwards for me...

Regardless, if you're looking for a longer lasting effect without that retarded feeling I suggest eating it. THC is fat, alcohol, & oil soluble so it's best used in butter, milk, alcohol, & oil containing recipes. I recommend trying to make some cannabutter and put that into some cookies. My favorite is my own recipe I like to call Forghetti: melt some cannabutter over a small plate of cooked spaghetti noodles & toss in some parmesan, italian seasoning, garlic, crushed red pepper, etc...