Incident metadata and transcripts are stored in a PostgreSQL db indefinitely. We've logged over 250k incidents since January. Planning on combining the incident data with other sources for historical analysis, search and such.
I like that you're adding historical analysis - it reminds me of some similar ideas I've seen in the past, like the opportunity atlas (https://www.opportunityatlas.org/) or the roadway report (https://roadway.report/beta).
you could also add colored markers to filter by incident type, frequency, etc.