I didn't think this was really needed but apparently people have been using a list which was once included as a Pi-hole default but has been unmaintained since 2018, and thought everything was fine.
I don't know how the exact answer the question "how long is a long time"? But clearly somewhere less than 6 years would have helped in this situation.
Edited to add: Maybe a heatmap could be used similarly to the network table. Greenish colours indicating recent updates through to red for clearly stale files at whatever time that was decided to be.