This had to have been only for FAANG companies right? I'm not saying it's unheard of, but I've done dozens of interviews and I've never had more than 1 all day on site. I'm not even sure anything else even justifies it in terms of time spent interviewing and compensation levels.
None of these were FAANG companies. This was long before FAANG was a term, btw.
FAANG companies, even 3-4 years after the dot-com crash, were 8 something hours - but over a single day, all at once. Grueling to put it mildly. Though lunch was in there too.
The other companies were pretty mellow comparatively, but did take longer.
The one I ended up working at (small no name company in the midwest), I flew out and spent 2 days interviewing and negotiating with.
