Browser caching is an important part of Fiori Launchpad performance, as it's explained in the following SAP notes:
#2447857 - Fiori Launchpad: How to check browser settings for better performance
#2421371 - Understanding Launchpad performance Issues
There are two types of resource available in the Firoi Application .
There are "static" resources like MIME, js, css, that need to be fetched once (on the first launch), after which they are untouched for the duration of the caching .
This is the data that is retrieved via odata services. The odata service are call each time data is request from the backend , this is not cached to ensure that the data is current.
->If an application is loading slowly even when caching is on this maybe due to issue getting data from the backend via odata service.
This can be confirmed by running a HTTPWatch trace and filtering by the longest time . If most time is spent on static object caching may need to be activated. If the issue is with odat service this needs to be checked further.
Whenever you experience slowness, it should be investigated in debug tools of your browser, which resources are slow to load.
With proper caching the static resources should not burn too much time.