Thanks all. The sales agent who they've been working with said customers have up to 3 months, so since they handed business operations over on 1/21, I think this means that on 4/20 they should be able to close out their account permanently.
One other question though: with these chargebacks, is it possible to request that the processor send out invoices instead of debiting directly from their account? The main thing here is that they don't want to keep their account open due to suspected fraud which may or may not be directly to the current credit card processing company and their agent (we feel iffy about this agent of theirs, so we also don't want to show our hand and tell him we're closing the account, lest he tips it off etc).