Why you should play 15+15 Classical

I had my first tournament few days ago and just to prepare, since it was 25min 5d control, I played about 20 15+15 Classical games.

I normally play 5min or 10min.

After playing about 20 Classical games, I have realized something very very important.

When I lose in Classical, I don't get upset or frustrating. (Not sure how to explain this)

When I lose in 5min or 10min, especially when I'm winning and I lose by time, I get upset and frustrating because

*I blundered
*I missed a mate
*I didn't see the opponent's piece hanging
*I left my piece hanging
*I didn't see the better move that I normally would

Imagine there are two men who try to lose the weight.

John and Jonathan.

They both decide to do 50push-ups, 50 situps, and 50 jumping jacks

John - He does 5 pushups, 5situps, and 5jumping jacks, and does this one set every hour throughout the day

Jonathan - He does 25pushups, 25 situps, and 25 jumping jacks, and does this 2 sets 30mins apart.

Which person would lose the weight faster?

When you are a beginner and want to improve but only play like bullet or blitz, it's like you do 5 push ups and stop. Then expect to see a great result, but you won't.

When you play Classical, you squeeze your brain out to come up with best move possible, and when you DO come up with such a good move, that move gets registered to your Chess Vocabulary.

You have to register lots and lots of chess vocabulary in your chess brain to improve.

By playing classical games* you improve you chess. By playing blitz you check your shape, test some opening ideas, practice pattern recognition and have some fun. So both is good, depending what you need.

*of course, you would have to analyse your games afterwards, first without the engine and then with the engine

Time control are getting faster and faster and nowadays calling a 15+15 "a classical game" is ridiculous. That's how lichess sees it. You will not do that much thinking in a 15+15 game. To really analyse and evaluate a position, you need at least 3 to 5 minutes. So in a 15+15 games, you will be get a chance to evaluate the position 5 times! You will not get a "quality game" with that. I would go for a 60min+10sec to really get a chance to sharpen your skills (thinking process, analysis, evaluation).

...damn I missed the checkmate in 1 (captcha)

If you look at OTB tournaments, the increment time for long time controls is 30 seconds.
A semi-rapid is what +15 seconds of increment time.
The initial time to play out the game is 90 minutes.
A semi rapid is around half that ... 45 minutes.

So if a person wants that semi-rapid feeling of OTB... then 45 minutes + 15 seconds is half of that OTB slow time controls.
You're not writing the chess moves, so you don't need that 30 second increment time. Reducing the 45 minutes is going to bring it closer to a rapid game. I would leave the +15 seconds for a semi-rapid game.

Pondering can be done on increment time and never need the initial time. It all depends on amount of experience and type of time control that you need to play well. If you feel the stress of time, then increase your increment time, not the initial time. If at the end of a game your initial time is larger than what you started with, then play with less increment time. You want to see the time go down, but not down to near zero to get stressed on time.

Playing classical help you with your standard games.

Play more long games (60 at least) than rapid (less than 60 !)
Try 5+5 for example to test your opening knowledge until the 10-15th move

play most of your games against stronger players (+100 to +150 elo) and some games against -50 to -100 elo players

15+15 is enough in my opinion. I have never seen a beginner that needed more and I have taught chess to quite a few people by now. The reason why I would not start with a game thats longer than an hour is because people with less than 1600 typically can not put that time to good use. I learned the most through 30 min OTB games and 15 + 0 here on Lichess.