From the STORM dashboard click on Websites
On this page you will see a list of Websites that you currently have set up on your Nimbus server. Click the cog icon next to your website to manage your website.
Click on Configuration.
Scroll down to the bottom and you'll find the Browser Cache Expiration Time
This is set by default to 1 Month but can be changed from 2 hours to 12 months or even to Never and a variety of lengths in between.
The Browser Cache Expiration specifies how long static resources will remain on your visitors' computers, this reduces load time of the site after the first initial visit as less resources need to be downloaded on subsequent visits.