I don't really do any general practicing anymore, unless I have to prepare for a new video/recording. Then I usually play for around 20-40 minutes at a time, a few times per day, until I feel like I can do it comfortably. Let the brain figure it out while you're doing other things!
It's hard to say when I started playing. I've never taken lessons or anything, so I've gradually become better and better since I was young. We had a piano in our house at some point, so that's probably when I started playing a bit. And I got my first guitar when I was 14 years old. So, at least ten years for both.