Azure CDN Miss Large Blob Storage Egress?

Azure Blob Storage has Azure stock CDN serving general web delivery files (jpg/png/txt/pdf).

A configured Storage egress alert fires generally once a day that over 300mb of data has left Storage.

Taking two views, one showing CDN response size vs Blob egress, and another showing CDN request count vs CDN byte hit ratio, seems to show that the CDN is regularly in a “cache miss” state and the end-user is getting content from Storage.

Can anyone corroborate that I am reading these graphs correctly?
What is the best way to ensure that everything is cached all of the time? Content probably changes 1% a year and is added-to 5% a year.