I was involved in a single collaborative post anywhere near that length. It involved four people, and took us 10-12 hours spread across two weeks. By the time we got it up, the RP had died because holidays. Also, it was a RWBY RP and I haven't managed to join one that survives past the initiation event yet.

EDIT: Now that I've gone back to look at it, I don't think the collab I was in ended up being even half as long as Seraphs' example.