eeyore888,
You might like to say what the speed and type of CPU in your computer, also the size of the hard drive and how much spare space is left.
You can try clearing out your browser caches, and your temporary files, also defragging the drive can help. Fairly obviously it is best to do the scan with an absolute minimum of other software running, and the browser closed, but you probably already know that. I also turn off teatimer before I carry out the weekly scan.
What you can try is going into Spybot, and with it in Advanced mode, click on settings, then settings again, then scroll down through the settings screen until you find the System Start group. Click on "Run program once at next system startup", then exit Spybot and reboot. Spybot will start up early in the bootup sequence (once off setting). Compare the time taken to do the scan in comparison to the other scan times you have been getting.
You have not said what AV software you have, and some users have reported very significant reductions in Spybot scan times when their AV is disabled. Obviously you would only do this off line, and then re-enable the AV again after the scan.
Please post back and let us know whether some or any of the above has helped.