Six hour-long segments is pretty far from abnormal.
Homework - especially anything before the rest of the process - is absolute bullshit. If you're not also investing any time in the interview, you can compensate me. My time is not less valuable than yours.
I did once spend an hour or two putting together a presentation for one prospective employer - it was attended by several engineers and managers over the course of a half hour, so there was still reciprocation - but I declined to perform the at-home coding exercise at the end of the process.