Performance issues due to excluded expiry dates

Our client continues to be discouraged w/ this theme because of performance issues.

Using Google PageSpeed Insights, GT Metrix, etc., we are having trouble with file caching.  We have tried almost every caching plugin per your suggestion. The problem with caching is that BuddyPress is a membership website and outdated content can appear to logged out users. Also, if I understand correctly, caching plugins will attempt to cache entire pages, but not necessarily specific files.

There are certain files that we can cache such as CSS, js and images and we plan to integrate a CDN for these files soon. However, your theme file fails to natively include expiry dates/maximum age in the HTTP headers for static resources, such as the site logo file, icomoon.ttf, js and css files, and featured images (posts and pages). Can you provide specific instructions on how to set expiry dates on theme items or correct the theme to do this in the theme options or elsewhere? After all, there’s never a time where the site logo will change every few minutes (for example). Even using a caching plugin, I believe your code fails to generate the site logo, font files, etc. without expiry.

Please advise.