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.
He appears in the same fashion, but I could not find a good video that wasn't bloated with graphics/misinformation to link.
*It was 2 AM PDT when we were observing DST, so when the clocks move ahead an hour in the spring, the time will likely return to 2 AM PDT.