Does anyone do more than 4 x 8

People talk about 4 x 8’ intervals at +/- 104 - 108% of FTP or +/- 90% max HR.

Does anyone do more, i.e., 5+ x 8’?

Some people do. You can search yourself.

Filter by threshold, overs, Level 5 or more. Click on a workout. At the bottom, there’s a link to see all past public rides.