Could each of those programs be producing cache or 'scan history' files, thereby eating up disc space?
Yes potentially
https://forum.avast.com/index.php?topic=97815.0
- avast! Log file locations:
- Windows 2000, Windows XP - C:\Documents And Settings\All Users\Application Data\Avast Software\Avast\Log
- Vista, Win7 - C:\ProgramData\Avast Software\Avast\Log. Some may also be in the respective \Report folder.
But as far as I'm aware there is no setting where you can change the log file locations.
or
As of 04/20/2014, and with Win 7 Ulltimate 64-bit, I'm finding my Avast! log files here:
C:\Users\All Users\AVAST Software\Avast\log
This is good coding practice because Microsoft discourages using the installation folders for installed programs to store such data. Instead, locations like the one above are preferred.
Of course, MS is the first to break their own rules. ;-) MS SQL Server, for examples, stores its database files under its installed folder.