It will depend on which report you are disputing. If you paid for the report, the clock starts to run on the day they receive the dispute and they have 30 days. If you dispute information based on your "free annual" report the period is 45 days.
I would urge you read very closely 611(a)(4). You will find that all the CRA needs to show is they 'considered" the information you supplied.
Further, regarding the burden of proof to show willful non-compliance, have you read the latest
amicus brief from the FTC on this very same issue?