You never wait for the chargebacks. If you get chargebacks, they cost you a lot.

You try to detect/block immediately - if a thief wants to check 10 cards in 5 minutes, you want to block him in the middle of it. And you immediately revert/cancel any transactions that succeeded so that you don't get chargebacks.

It's actually usually way too late by the time the chargeback rolls in. Proper villains will have moved on.