Wow you guys use a lot for root.
My home partition is on the root directory.
matthew-S206:/home/matthew % df -h | grep "/$"
/dev/sda8 15G 12G 2.4G 83% /
However all of my main folders are actually symlinks on a storage partition and that is where most of my data is stored.
matthew-S206:/home/matthew % du -cshPx ~
My home directory is really a dumping ground for things until they are sorted out.
matthew-S206:/home/matthew % ls -l | grep "^l"
lrwxrwxrwx 1 matthew matthew 35 Dec 28 15:03 Documents -> /home/matthew/storage/my_documents//
lrwxrwxrwx 1 matthew matthew 35 Dec 28 15:06 Downloads -> /home/matthew/storage/my_downloads//
lrwxrwxrwx 1 matthew matthew 31 Dec 28 15:01 Music -> /home/matthew/storage/my_music//
lrwxrwxrwx 1 matthew matthew 34 Dec 28 15:04 Pictures -> /home/matthew/storage/my_pictures//
lrwxrwxrwx 1 matthew matthew 32 Dec 28 22:04 Public -> /home/matthew/storage/my_public//
lrwxrwxrwx 1 matthew matthew 31 Dec 28 14:59 Videos -> /home/matthew/storage/my_video//
So my root directory is 15G with ~ 8.5G used for installed apps etc.
20-40G should last you a lifetime Then again, i'm not a gamer and they take up space.
Indecently 15G for root is big for me but that is because i decided to keep /home on root.