Some things to consider:

It would be difficult to describe a "typical" hallucination, as these experiences vary considerably in length of time, quality, and sense or senses affected. Some hallucinations last only a few seconds; however, some people diagnosed with Charles Bonnet syndrome (CBS) have reported visual hallucinations lasting over several days, while people who have taken certain drugs have experienced hallucinations involving colors, sounds, and smells lasting for hours. Albert Hoffman, the Swiss chemist who first synthesized lysergic acid diethylamide (LSD), experienced nine hours of hallucinations after taking a small amount of the drug in 1943. In 1896, the American neurologist S. Weir Mitchell published an account of the six hours of hallucinations that followed his experimental swallowing of peyote buttons.
hallucination: Definition, Synonyms and Much More from Answers.com

You'd have to do a lot of weed, or hash, to reach these levels - if it's even possible. I've heard of people smoking large amounts of hash continuously for hours, and maybe that would be similar but I doubt as strong or "real".