> An 8 hour interviewing day plus an hour on the front end (screen) or back end (confirm/double check some things/really meet manager) can make sense.

> 3x 3 hours sounds -exhausting-.

I think most people would prefer 3 x 3 hour blocks.

A 3 hour block could be worked into a day without anyone batting an eye at every (tech) employer I've ever had. People go to appointments all the time.

A full 8 hour interviewing day requires taking the day off. It's also exhausting to do it all continuously.

The 3 x 3 hour structure also allows the company or candidate to end it early if it doesn't look like it's going to be a fit. I'd rather lose 3 hours and than take a vacation day, spend 8 hours somewhere, and then get rejected if they knew I wasn't a good fit after the first few hours.