Directories can be kept tidy by running the SWATTidyFilestore.pl located in the <installation directory>\webapps\ServiceSWAT\perl directory.
The command line for this is
perl SWATTidyFilestore.pl <no of days to keep>
<no of days to keep>, any files older than this many days in history will be deleted.
To ensure regular cleaning it is suggested that this is run as a scheduled task.
Because the log file is constantly written to, its last updated timestamp will always be recent it will not appear to age, and therefore is unlikely to be tidied automatically. This file can therefore be very large.