Use Better Cache to optimize Firefox bandwidth consumption.

A lot of users use internet schemes with restrictions on the bandwidth consumption. Firefox re downloads all the heavy files even if they are in the cache ( Even if the cache size setup way too high ), this will considerably increase your bandwidth consumption. It’s very annoying to download the files again if you already have them in cache. Re-downloading the files that are already in cache will considerably decrease your browsing speed.

A very good way to save the bandwidth is to install Firefox Plugin called BetterCache
Open this page and click on install the Plugin. Restart Firefox then click on tools > add-ons. Click on the options for betterCache Plugin. Check the radio button next to never, under check pages for actuality. This way Firefox will avoid looking for new versions of the pages or elements.