Pretty sure a 20 year old beginner is not going to be a GM after 6-7 hours a day for 8 years.
Sure they'll improve a hell of a lot, but if that's all it took there'd be a lot more GMs (and IMs).
If that's all it took?
Are you serious? 6 hours of practice every day for 8 years is like what... 17.000 hours of practice? If the practice is even somewhat structured, I don't see any reason why one couldn't become a GM like that.
Yes, that's a meager amount of practice.
And you only think you'd be a GM after it because you're terrible.
I didn't even check your rating or read the rest of your post.
Pretty sure a 20 year old beginner is not going to be a GM after 6-7 hours a day for 8 years.
Sure they'll improve a hell of a lot, but if that's all it took there'd be a lot more GMs (and IMs).
If that's all it took?
Are you serious? 6 hours of practice every day for 8 years is like what... 17.000 hours of practice? If the practice is even somewhat structured, I don't see any reason why one couldn't become a GM like that. The real question is, does anybody in their right mind have the time and willpower for that?
Most adult beginners have other things to attend to, like work and responsibilities. Kids usually do too, at least to some extent (like school, other hobbies, spending time with family and friends), but they have something that adults don't - years to practice. A kid starting to play chess at age of 7 can muster almost 10.000 hours of practice by the age of 18 simply by playing/studying 2 hours a day. Whereas someone starting at age of 22 would be 33 by then. So adults have to compensate that by studying and playing more hours each day. And frankly, majority of people don't have that much time - or willpower to spend all their time for such an unilateral goal like chess mastery. Most people who have the necessary dedication and willpower to pursue such feats usually decide to focus their attention towards getting a university degree, PhD or put a lot of effort in their work or a business. Something that is undoubtedly going to benefit you in the long run, whereas becoming a chess guru doesn't really open that many doors for your future.
So I don't think that the lack of examples is a good enough proof, that adults couldn't make it to master (or heck, even GM) level. It just doesn't seem like a reasonable goal for vast majority of people, and those who might have what it takes to do it, decide to spend their effort on something that contributes more to their lives.