1000's Of Files In Mozilla Firefox Profile

I use FireFox browser under Win 8.1. I see that in my profile for the browser there is a subfolder named cache2 and under that is one named entries. My question has to do with the 17,519 files in entries. A sample file name is 00AA290F1CA035A772BF1A97E84D5C99FBFAD80C. None of these is very big, just the quantity of them. And they are all dated within the last 3 days. Are these all necessary and do they disappear after a few days, being replaced by new ones of the same name? Thank you

 

~350MB 0f cached files (saves downloading again on page refresh) is normal for modern browsers/connection speeds - 'road warriors' might benefit from ~350 - 1000MB, depending on connection speeds when away from base.

~10+ years ago IE7 might have used 2GB+ default even from a static location/connection. Cache size can be controlled per browser. ~350MB is fine for most users/slow-average connection speeds.