"Musician Time" is one of the most frustrating aspects of dealing with musicians. Load in time says 7 so, the average person would assume you should show up at 7.
Bands and everyone start sauntering up to the venue maybe 7:45 to 8. And this happens every time. Being as punctual as I am, this constantly drove me insane. It wasn't until I read Zimbardo's The Time Paradox and took a class on international strategy that I finally got it.
People's different beliefs in time affect their behavior and interpretation of the world. The conditions someone live and work in shape the person. It's simple, but often overlooked.
In Project Time, a product is done when it is absolutely perfect and has spent the last few months being tweaked. This is why albums take so long to put out, there's no concrete schedule (in most cases) other than when an artist thinks his work will be "ready'.
In Linear Time, a product is done when it's time to ship. This would be many business situations, where if you don't ship your product on time you're out of a house. Sure, there'll be bugs, but it's more important to be on time.
(Roughly) Most musicians live in Project Time, and most businessmen live in Linear Time. Being aware of the time perspective of who you are dealing with will make life much easier. Always understand how these differences in time perspective may affect people's behavior. If you think linear, (like myself), it's easy to get frustrated that nothing is ever on time with music, but by understanding the project viewpoint of "hey, as long as I'm on stage when it's stage time, we're good" it makes it much easier to work with.
Regardless, I'll still be waiting outside the venue at "load in time". It's how I think.