This depends on alot of shit man, first if your high is only 30 minutes long, your smoking shitty ass weed. Second, your not smoking enough weed, if you smoke a small bowl its likely to not last too long out of a pipe, especially if your weed is no good. And it will make you tired. Ive smoked some really good shit that doesnt make me tired at all and it lasts hours.

Another tip: get an energy drink, it does the trick when your all burnt.