2 years for me.
I do it for disease prevention as i don't have any specific health issues.
That's smart by you, a ounce of prevention's worth a pound of cure! I wasn't smart enough to see trouble coming, but having a serious health scare was exactly what I needed to get myself sorted out. I worked on the road so I ate allot of crap, drank way too much, generally didn't take care of myself. I guess when I was young I could get away with that, but it caught up with me. I've since retired and although I never got fat, I'm in better shape then when I was in my thirties, workout like a fiend, do saunas daily, currently into Wim Hoff's cold therapy/breathing methods.
I don't think any one diet is good for everyone, but for me Keto is a great diet, I don't even have cheat days, my wife can bake up some pretty great Keto baked good when I need something sweet. If anyone has blood sugar issues I highly suggest you look up Dr. Jason Fung on Utube, he's a Toronto doctor who's reversing Type 2 diabetes is people who've been on insulin all their lives simply by removing carbs from their diet and intermittent fasting.