Local server not reflecting updated files

I’m fairly new at user local servers. I’m using the http-server which is a package from Node. I’m using it to host an HTML5 game using the Phaser library. I have image assets I’m using in the game, and I sometimes update these assets. When I do, the changes to the images aren’t reflected in the game. I’ve tried restarting the server but that doesn’t help. It usually takes some time for them to update, maybe about an hour. Any ideas what’s going wrong?