My story is identical to yours.

I believe that anti-virus software installs viruses on people's computers just to make themselves feel useful. Anybody with anti-virus software always gets them. People without them (like me and Ben, here) never have any trouble. 

Heh... that's quite an interesting conspiracy theory samuel about AV programs bundling in viruses....

Basically if you aren't an idiot online you'll be fine without regular virus scans. My personal vista computer has no problems.

When Ever Norton or Spyware feels like it.
The norton checks are wayyy too long
and the spyware checks don't happen too often.
YES! i have two. softwares protecting me.

i heard trend micro is best security

i have no idea.. it just does whatever the hell it wants.. it might be scanning right now

you have to be careful with viruses, it's not just by visiting dodgy sites that you can get them. There are plenty of exploits around that can hide themselves in ad banners, facebook applications, etc.

Recently there has been a huge amount of SQL injection attacks that caused many big sites (coles online shopping, department of defense, etc) to start serving trojans to visitors.

Don't think that just by visiting only trusted sites you're safe from viruses. Keep your definitions up to date!

I rarely scan for virus maybe once every 3months , but I scan for bots and defrag my computer 1-2times a week.

Never, Mac and Linux on all systems here.

Mac desktop
linux laptop

viruses = epic fail

I always have auto-protection off; I scan my computer at least once every 2-3 days though, mostly for spyware.