my first job at a startup (first engineer after the founders) consisted of 13 hours on the phone with the CTO over a few weeks and then an in person all day interview that included traveling from Chicago to SF and a couple of dinners with the founders. this was 1996. our typical interviews after joining were all day affairs and they people almost all people that were referred in or had worked with in the past (I wasn't).

interviews at twitter back in 2010 were 6 hours and that was true even for me when we had an agreement to acquire my company pending the success of those interviews. at the time they had a lot of ex-googlers and they were setup similarly.