Hello BlebNevus
Maybe other people see the little extra time the program takes to do the virus scan as a sign that the program is doing what it is supposed to be doing and that is protecting your computer from the malware that is out there. Look at it this way. If Norton's wasn't protecting you as well as it is and you got some malware on your computer, it could and would take more than the little extra time it takes to scan the computer to clean up your computer and get it to the point where you can use it again.
If the problem is the amount of time it takes to scan, you can schedule the weekly scans to run at a time when you won't be using the computer and won't mind how long it actually takes.