The first time I did them was at a huge house party in high school. I just mowwed a whole bunch down.
I ended up crawling around the house with a flashlight somebody had given me for most of the night, and the backyard. Had a great time.
At the same time people can't handle crowds sometimes their first time. IT gives them anxiety and anything that gives you anxiety is something you want to avoid when tripping.
If you've never tripped before and are planning your first time somewhere where there are a lot of people, I would go with a low level trip. Things will get weird, but it won't be very intense. And you shouldn't have any problems being somewhat normal and social.
Also a good thing to remember kids. You can always eat more. You can never eat less. Make sure you're patient for things to kick in. Sometimes you don't feel it, you don't feel it, you eat a bunch more and as you're eating more or right after you start to come up hard, and you're like fuck, the shit you just ate hasn't even hit yet.
That can make things super super intense which can get scary, especially if it's your first time, and it can also give you anxiety on the come up, which could really make things suck.
Yes they can last for 6 hours, you'll probably end up peaking well before that though. Also you might feel an afterglow even into the next day.
Yes they'll last till the next weekend.
Again, just don't eat a bunch. If you're doing it with friends it's not a contest. Just because somebody eats an 8th or more, doesn't mean you have too. Do what you feel comfortable with, because if you feel good about it coming up, that greatly increases your chances of having a positive experience.
Avoiding small places, or being stuck places is key. If you go to a show and it's crowded with people, you're tripping, waiting for the band to come on, you can't leave, that can make you have a shitty time. IF you're at your friends basement doing them, and have no where to go, and your friends are going anywhere, you can feel stuck there.
Sometimes a little venue change, music change, conversation change is all you need.
Probably the most important thing is to be with good people. Being with good people will make any experience better. For tripping, it's almost necessary. The best option is to have somebody who's familiar with tripping around. If you're with an experienced person, they can be massively helpful at talking you down, bringing you on an adventure, changing the music to the perfect tunes, or anything else to change you from feeling scared to feeling FUCK YEAH!!!!!!
Best of luck. Happy Trailzzzzzzzzz