The Log settings allows you to set how long the logs are stored within PAS and how often they are cleared. By default PAS will keep log records for the last 30 days deleting the oldest logs at 24 hour intervals.
To open the Log Settings dialog:
Keep Records (days) - Number of days log records will be kept in the database. Records older than the specified number of days will be automatically deleted.
Delete Interval (hours) - The interval at which log records older than the specified number of days will be automatically deleted.