Related to that is ongoing work to make the field visible in the UI HDX-4894 - Getting issue details... STATUS .
As data freshness collects a lot of metadata, it could be used for more general reporting. If needed, the list of metadata collected could be extended.
Even for datasets which have an update frequency of "never", there could be an argument for a very rare mail reminder just to confirm data really is static.
For the case where data is unchanged and we have sent an overdue email, we should give the option for contributors to respond directly to the automated mail to say so (perhaps by clicking a button in the message).
The amount of datasets that are hosted outside of HDX is growing rapidly and these represent a problem for data freshness if their update time is not available. Rather than ignore them, the easiest solution is to send a reminder to users according to the update frequency - the problem is that this would be irrespective of whether they have already updated and so potentially annoying.
Another way is to provide guidance to data contributors so that as they consider how to upload resources, we steer them towards a particular technological solution that is helpful to us eg. using a Google spreadsheet with our update trigger added. We could investigate a fuller integration between HDX and Google spreadsheets so that if a data provider clicks a button in HDX, it will create a resource pointing to a spreadsheet in Google Drive with the trigger set up that opens automatically once they enter their Google credentials. We may need to investigate other platforms for example creating document alerts in OneDrive for Business and/or macros in Excel spreadsheets (although as noted earlier, this might create a support headache).