Eight hours is the standard, and it's California's number, not the school's. Every DMV-licensed traffic school teaches to the same state requirement, which is why "fastest California traffic school" ads are selling something the license doesn't permit.
The online wrinkle is that California regulates internet courses by content volume rather than a running timer, mandating the amount of material a licensed course must contain. Practically, that means your real completion time tracks your reading speed: quick readers genuinely finish faster than the nominal eight hours, slow readers take longer, and the final exam waits at the end either way. It's the one state where "how long does it take" honestly answers "how fast do you read."
The deadline around the course comes from your court: your notice sets the completion date, and the school reports electronically once you pass. Between saved progress and the court's window, the sane pattern is a few sittings, not a marathon.
Every DMV-licensed online school we track is compared on the California page, and the once-per-18-months rule on using it is on our frequency page.