He appears at *exactly* 1AM PST on Friday, and leaves at *exactly* 1AM PST on Sundays.  It does not matter what you are doing client side, he will disappear at this time.

[Watch him vanish](https://www.youtube.com/watch?v=vY08eITOUIw&t=10s).  

He appears in the same fashion, but I could not find a good video that wasn't bloated with graphics/misinformation to link.