Norton can be a real resource hog and really slow a system down. I wouldnt say a system is "optimized" either after a norton "check up". Ive seen systems that were almost unresponsive, come to life after norton was removed. We see many infections in our shop, and usually the only ones running a paid antivirus to no avail were using paid mcafee or norton. I see much better detection rates and less slow down with Eset or Kaspersky.