The advantage of the 90 hour start, which I didn't fully appreciate until 2019, is that the wind dies down when the sun goes down. I started in the first 90 hour group and it was brutal, between the people that wanted to set a record (why not the 80 hour group then?) and the wind. And it took 3 hours before the wind died down to a reasonable level. I have thought about doing 84 hours, but never have for various reasons.