I had used Windows Defender for a long time and I had never been infected. However, I am really cautious when it comes to downloading files from the Internet.
Just like me, I have my setup until now which is 2 years old and have windows 10 installed on it. I didn't installed any AV but relied on windows defender.
Knowingly on how you are easy to be penetrated by those viruses depends on your usage. I don't download random files as well specially those TOR files.
I have recently switched to Malwarebytes Premium and I am satisfied with its real time protection, especially the web one.
Been hearing good reviews on Malwarebytes, I might try this on my 2nd setup.
Malwarebytes is a good program, also the only 3rd Party program I would ever scan my PC with really. You should try it!