If you're thinking of archiving the game via GOG's offline installers (i.e. the one reason to buy specifically from GOG), you're going to have a rough time. Larian has released a couple totally broken offline patch installers that demand 1TB+ (yes terabytes) of space to work. Except they still don't work, even when the game and patch are on a drive with enough space. They've also created dead end upgrade paths because they never released patches to join the branches they created. Basically, plan on not being able to rely on offline patches, and instead expect to be downloading 100+ GB full installers if archival is your goal. Larian is well aware of the issue, and is either incapable of or uninterested in providing consistently working offline patches.
