The regulatory requirement is that a lender can use an existing FHD if it is less than seven years old and if there has not been a map change. Your FHD will reference the specific Flood Insurance Rate Map (FIRM) used to make the flood hazard zone determination. If that FIRM changes, they you would need an updated FHD form in file.
A lender is free to document this in a number of ways according to your own internal policies. That might include 1) pulling a new FHD, 2) internally reviewing to ensure the map used on the FHD has not been updated by using the FEMA Map Service Center (https://msc.fema.gov/portal/home
) and making a notation on the original FHD regarding the review, or 3) using an update feature provided from your FHD provider.
Any of those would be acceptable.
The fact that you might be notified if a property goes into or out of flood zone however may not mean that a map has not been updated, if the flood zone of the property has not changed with a map update.