How long does the effect of shrooms last?

The effects of Psilocybin (the actual drug within the shrooms), in my experience, last about 4 hours. It's a fairly mild trip, unless you take too much. For your first time, I would be pretty conservative with your dose (maybe half an 1/8). The problem lies in that since LSD is cheaper than real mushrooms, sometimes dishonest drug dealers (if there is such a thing) will soak regular mushrooms in LSD so you will trip, but it will last much longer, maybe as long as 8 hours. LSD isn't as "safe" but they're both with their dangers. You need to be sure you're doing this with someone you really really trust.

Natrual lsd High and at least 4hours. Get your life in order and stop try these drugs.

depends on the amount you ingest. Shortest length would be 3 hours... longest would be 7 to 8 hours. As you appear set to do it, I would suggest you make sure you are in a safe and happy place when you do it.... otherwise you could have a bad trip and that could end very very badly for you. Also realize that everyone is different and how you react to something like a shroom could be very different than how you've heard of it working with others. Also realize that it makes a difference if you are talking about eating fresh ones or dried ones... drying them breaks down the chemicals that your trying to take... likewise make sure you know what a shroom is or you may end up eating a death cap and that would end with you pushing up daisies. Now if your still going to try it... "party on dude".