Additionally, if you install Deficons, you might also want to install HappyEnv. This replaces your RAM:Env assignment with a dedicated device driver that is optimized for small files and implements a "load on first request" policy.
Without it, everything in SYS:Prefs/Env-Archive/Sys is copied to ENV:Sys (which is in RAM) on boot. If you have many default icons, this both wastes memory and slows down your boot times. HappyEnv mitigates this considerably.