To add on
@daisy_yawn's comment, I would say use all 10 days to prepare for ACs generally but 2-3 days for AC-specific questions (i.e., why us, their recent deals, questions around specific practice areas) is enough if you're doing it full time. If you balance other obligations, I think around 4-5 days?
Having more time to prepare and think deeply about why you want to work at that firm + preparing specific questions you know will come up is always better than cramming in 2 days but it can be done if you're not planning on doing anything else other than work/eat/sleep/gym.
EDIT: it also depends on the type of AC you're doing. If it involves a technical component (i.e., A&O case studies), I think more time is needed.