SAS is a cracking program for a freebie! (note that you should always download the updates before doing anything else, unless you get the paid version which is automatic and runs in realtime).
It all boils down to how many files you have on your disk. To speed it up a little, run CCleaner first and run SAS using quick scan. Video files are a no no as they take a while to scan.
I have an external drive where all my music/video files are stored so the C drive only takes me 30 mins.
However, do a full scan say, once a week.