My machine has an 80GB HD, which isn't small, but it's not cavernous either. Every time I DL software updates from Apple, I see that the file sizes add up a bit . Seems like in a single update that consists of something for each iLife application I could be DL'ing as much as 1/2GB.

Is the system *replacing* old files with this new information, or is it simply *adding* this onto my machine...which will sooner or later end up in me surrendering a good amount of precious HD space for updates for some software that I rarely use?