Just dont delete it if your internet connection is low.
Cache Location for firefox :
1. Win xp : C:\Documents and Settings\*your user*\Local Settings\Application Data\Mozilla\Firefox\Profiles. sellect your profile. there is cache folder inside. after you loading all of your data game, copy cache folder and back up. So, when firefox crashes and delete cache automatically, you can restore your cache.
2. win 7 : C:\Users\*Your user*\App Data\Local\Mozilla\Firefox\Profiles
Cache Location for firefox :
1. Win xp : C:\Documents and Settings\*your user*\Local Settings\Application Data\Mozilla\Firefox\Profiles. sellect your profile. there is cache folder inside. after you loading all of your data game, copy cache folder and back up. So, when firefox crashes and delete cache automatically, you can restore your cache.
2. win 7 : C:\Users\*Your user*\App Data\Local\Mozilla\Firefox\Profiles