When I perform a system scan it normally scans 450k+ files and takes just under an hour. The last 2 times I have run a system scan, and I have changed no settings and deleted no files, it completes the scan in 6 minutes and only scans 230k files. What's going on?
Smart optimization can be enabled/disabled in the scanner setup. Speaking about the on-demand scanner, you can enable/disable it for particular profiles. In-depth scan has Smart optimization disabled.