Hmm, just realising that clients cache images for many days. Updates may not happen as frequently for everyone as I'd have hoped.
Following my dynamic image experiments, this image below will update in realtime, basically an evergreen post
h/t nostr:npub1hklphk7fkfdgmzwclkhshcdqmnvr0wkfdy04j7yjjqa9lhvxuflsa23u2k for the original code. Did you set up your bot for nostr already?
Discussion
Nostr cache systems should adhere to the http cache headers from the original media. If a media is no-cache, don't cache it.