I just started caching with Cloudflare, but if I check next day, most of my images are being expired.
DateTue, 29 May 2018 08:42:54 GMT
Last-ModifiedWed, 01 Feb 2017 23:52:23 GMT
ExpiresThu, 28 Jun 2018 08:42:54 GMT
curl -I https://example.com/file.jpg
First time it will result in a MISS, next time it will be a HIT. Same thing with metrix tests. First time it will MISS but HIT the next test.
BTW I have a cron job that runs every hour which hits the HOME PAGE, so the site is being accessed once an hour.