Of all the available tons of anti-malware software for Windows all over the internet, I've never used any paid solution(I am a student, I have no money). Since the last 10 years, my computers running Windows have never been hacked/compromised or infected so badly that I had to reformat them(of course I did reformat them for other reasons). The only program I have for security is Avast Home Edition, which is free, installed on my computers. It has never caused any problems; always detected malware, updated automatically, has an option to sandbox programs and everything else I need. Even if I got infected, I just did a boot-time scan with it, downloaded and ran Malwarebytes, scanned Autoruns logs, checked running processes with Process Explorer and did some other things and made sure I cleaned my computer. I am quite experienced and I've always taken basic precautions like not clicking suspicious executables, not going to sites which are suspicious according to WOT, and all that blah.

But recently I've been doing more and more online transactions and since its 2012 now, I'm doubtful whether I need more security or not.

Have I been just lucky, or do my computing habits obviate the need to use any more(or paid) security software?