Ignore the first 4 answers, Psilocybin Mushrooms can induce a psychedelic state for 3-6 hours. Generally the risk is psychological; you could possibly have a flashback or a terrible experience on them. Basically, it's an odd experience, but can aid you in perception and on reality. However, not everyone is meant to take a psychedellic; it can show you the best and worst aspects of life. If you want to take, have a clear mind and a very positive mindset. But no, it's impossible to trip FOREVER.. However, if you choose to use a psychedelic frequently, it can mess you up mentally. Generally, it won't mess you up, but be wary of frequent use. It could end up driving you insane.
Have tried Mushrooms and LSD.