From a data governance and data discovery standpoint it would be useful to have a badge to apply to layers and items similar to the "Authoritative" and "Deprecated" badges currently implemented. Something like this terrible markup:

This would be helpful to alert users to the fact that they are using data that is older, but still valid for a particular time period. For example, if you wanted to find roads data from 1993 it could be marked "Archived" and then users would be less likely to use out-of-date data in their projects and analysis.