Every day I usually play one or two 10+5 games for fun and to try to train my decision making. 10 minutes seems to be the recommended time control for a beginner. However, for a long time I've felt rushed with 10 minutes. I get in the habit of running out of time and making "lazy moves" since I feel like I have to play something. Is it better for me to play 30 minute or hour games, or even longer (one sitting) against a computer, to be able to "think through" and be more confident in my strategies? Or is that too long for beginners to focus and counterproductive to being decisive in actual games?
Maybe try increasing the time control in increments, until you find something that gives you meaningful games. 10+5 isn't really blitz, but it also doesn't feel like a typical rapid game. I'd recommend moving up to 15 10, 25 5, or 30 0, and see how you like those. 15 10 is fairly popular online, and the latter two are generally accepted as the main "rapid" time controls in OTB tourneys and such.
Everything depends on your goals.
The first that we need to accept is that bullet chess, every player has 60 seconds for the entire game, and classic chess are not the same game. Bullet and classic chess share all the rules but the time. In a similar way that the 100 meters, or 100-meter dash, is a sprint race, and the marathon is a long-distance foot race with a distance of 42.195 kilometers.
Nothing wrong with bullet, blitz, or correspondence chess, but it is important to understand that they are not classic chess (By the way, correspondence chess is in the other side of the spectrum, you can use a day or a week, and sometimes a month to make just a single move).
If your goal is to learn in depth classic chess, my advice is that you play just classic chess and correspondence chess. www.lichess.org calls classic chess when you play 30+0 OR MORE (30+0 means every player has 30 minutes for the entire game, a maximum of 60 minutes in total).
Most of the people argue that they play quick time controls because they do not have too much free time. However, the facts contradict that claim because they play an hour, sometimes two hours, and even more.
The truth is that bullet and blitz are more popular because you can always blame the time if you make a mistake. Also, if you play 10 bullet or blitz games, if almost impossible, from the mathematical perspective, that you lose all the games. Every time that we win a game, no matter which game is, our brain produces dopamine and we feel great. Maybe the greatest benefit of quick games, from the psychological perspective, is that if you make a mistake and lose for that reason, you can start a new game and you will forget the mistake because you are playing a new game. However, to improve in classical chess, we need to discover and remember our mistakes to try to avoid those mistakes in the future. That is why classic chess is so hard from the psychological perspective. Another bad habit that we get from speed chess is that we learn to play fast, and many times that produces big mistakes in classic chess. Nakamura would have played the world championship final against Nepomniachi but he played fast and lost against Ding Liren. Nakamura is the most famous speed chess player in our times, after Magnus Carlsen, of course. Some people, like Magnus Carlsen can play speed chess without a bad effect in classic chess, but we need to remember that Magnus is a genius. My final advice is that you select one time control, no matter which time control is, and play ONLY in that time control.
The answer is already in your question:
I've felt rushed with 10 minutes. I get in the habit of running out of time and making "lazy moves" since I feel like I have to play something
This is completely normal as a beginner. I remember being anxious when my opponents opened with 1. Nf3 or 1. c4 for quite a while, until I got the (false) sense of security by having an opening repertoire.
As soon as you have to rush and make lazy moves, this hurts your chess tremendously! You'll get the bad habit of playing lazy moves instead of the principled approach, which would require calculation. You'll never become a strong player if you avoid the difficulties instead of trying to think and figure it out. For example, when the opponent attacks something, do you defend it as soon as you notice it? Or do you check whether you have something stronger and calculate whether the opponent can really afford to take the piece? The difficult parts are what make you grow your chess skills. In particular, you learn more from the mistakes you make in your own games than anything else. But you can only learn to correct your thinking if you have actually thought about the move and used enough time.
When playing faster time-controls, players rely mostly on two very important skills:
- Intuition (you first must build that from experience in proper, long games! Not everything )
- Fast and accurate calculation and pattern recognition (this also needs to be trained. No beginner starts as a perfect calculator or knows all the patterns).
This explains, why you should know how to play proper chess first, before playing blitz or 10 min rapid games if you really want to improve your chess!
Or is that too long for beginners to focus and counterproductive to being decisive in actual games?
Not at all. On the contrary, it is a crucial skill to learn how to stay focused. It may be hard to focus at first, but you'll need it, especially for later in faster time controls. You'll be surprised how fast the time goes by if you truly dive deep into the position and think about your and your opponent's moves. I've had classical games, where hours passed like minutes.
Choose a time control where you do not feel rushed, even when you have already played quite a lot of moves, and always play with increment!
I would suggest playing 15+10, which you can play on chess.com or lichess.org. If you still feel that you had to rush some moves and couldn't think about everything enough in many games, play even longer time controls. Please note, that occasional time trouble is completely normal and part of the game. A major drawback of playing online only is that one is not used to playing "real" (i.e. classical) chess. If you do not have a club where you can play classical games, the best current alternative are the lichess 45+45 and lonewolf leagues.
You will also be much more proud of your classical games than on any random blitz or rapid game, where your opponent blundered something. The price of every move is higher, as you invested so much time in the game, but the reward will be even greater. Not only your happiness when winning a classical game, but what you learn from defeats as well.
The longer time control, the better, if you want to improve. Most streamers, GMs will advise you to play longer time control if you can to force you to make sound moves and not average moves that just put some time pressure on your opponent. As a 1800 in Lichess, I still struggle to apply strategy in 10+5 time. You can get a nice tactical level even if you play only blitz, but you'll never improve your strategy (long-term thinking, color complexes, unbalances, king safety, having a plan...) if you play blitz or faster. My favorite time is 10+5 (that's why I play on lichess) and I'm quite surprised that you picked it as a beginner. That's a great decision, but most people just do blitz for fun. (And that's fine if you don't care about improving). You need to find the most pleasant time control for you, so you'll be motivated to play chess. But if you select longer than 10+5, that's great ! You'll get more in-depth knowledge about chess, and not just tactics.