At our club there was an old guy who was very good at blitz (G/5) games.
He has won many blitztournaments with players U2000 rating.
But in long games he wasn't that good, he had only a rating of 1650.
The reason for that was that he hadn't the patience to think long, and his ego wanted to impress the opponent by playing as fast as possible. Often having only 5 minutes used of a G120 game.
It was not easy to play against him, because you had to realize that he deprived you from half your usual thinking time. You couldn't think in the time of your opponent, since he thought so little.
And there was a young lad at the club.
He only played once a week a serious game at the club.
He didn't study or something like that, but there was only one thing he did besides his one long game per week.
He played thousands and thousands of blitzgames with the old guy.
Below you see a rating graph of the young lad.
From september 1994 till september 1997 his rating went up from about 1520 to 2020. Which is 500 points in 3 years.
After that he plateaued. He has tried ever since (= the next 9 years!) every form of study to break thru his sealing. Without succes.
It has costed me a long time to find out what has happened, but now I think I can formulate it.
The old guy had a lot of tactical patterns in his LTM. If he hadn't had these two flaws in his character (impatience and impressing opponents by fast moving), he would have had a rating of 2000+. Due to the flaws he had only 1650.
The thousands of blitz games made that the young lad got a "copy" of the database with tactical patterns in his own LTM. Since he hadn't these flaws in his character, he became a 2000+ player with it.
One of the lessons that can be learnt from this is that it's ok to play blitz, as long as your opponent is stronger than you.
You can see that he plateaued almost instantenously. He was 19 years old by then.
I think there are two factors at play: first he ran out of new patterns, second he reached an age where improvement doesn't come by itself anymore.
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