var/cache/apt/archives occupying huge space

You don't need to keep them around if you don't want them. Executing a

sudo apt-get clean

will clean out the directory.

Seems like

sudo apt-get autoclean

is a better choice than

sudo apt-get clean

autoclean will only remove "useless" archives

From the man page:

Like clean, autoclean clears out the local repository of retrieved package files. The difference is that it only removes package files that can no longer be downloaded, and are largely useless. This allows a cache to be maintained over a long period without it growing out of control. The configuration option APT::Clean-Installed will prevent installed packages from being erased if it is set to off.

You can adjust settings in Synaptic package manager, menu Settings/Preferences, the Files tab. From there you can also delete the cache.