Not if but when it bites you, it likely will not be pretty.

You're rejecting dozens of not hundreds of ways to avoid having bad things happen, just a couple examples being having your identity stolen or losing data. These risks already exist no matter what you do, but they are several times more likely with every few months that you go without security updates.

Besides that, you will eventually be forced to update, either because your device dies and has to be replaced or because of something like software you require refuses to run on your 8 year old OS. When you get that new OS, the jarring effect will be much worse than if you just allowed your devices to evolve as designed. Updates are not a bug, they are an extremely valuable feature.

Your reasoning that it ain't broke so you don't fix it leads me to believe you have never written software. All software is inherently broken. Products under development for 30 years still have flaws so fundamental it's hard to even imagine. I say all of this as someone who has had his hard drive wiped accidentally by software bugs, had email and other accounts randomly hacked, and personally worked with broken ass software from the world leading giants. And as a software developer I can say for sure: all software, no exceptions, is barely working. No matter how solid it it seems, some random weird edge case can cause complete failure

Update your shit. It's not even that often that stuff breaks in (non Windows at least) OS updates these days