Passing the allowance can lock the account
The help center sends a notice when the account reaches 80 percent of the monthly unique visitor limit. The account can be locked after you pass the limit. Repeat overages can unpublish the pages.
“If you approach the limit of your unique monthly visitors, you will see a notice in your account when you are at 80%. If you exceed your traffic limit, your account will be locked, and your landing pages may be unpublished if you have surpassed your limit on multiple billing cycles.”
“A unique visitor is counted once per page regardless of repeat visits; the tracking cookie expires after 3 days, after which the same person can count again.”