I have hacked for a really long time without getting caught. I went as far as three months without a single ban, and if I wanted, I could go even further. I know some friends who have been constantly hacking for well over one or two years without any VAC Ban, just because they exploit the Overwatch system.
When I got banned, it was my own decision, I decided to hack non-stop during an entire night, and ended up doing approximately fifteen games while going full rage mode so I can get banned fast.