Then you're typing slower than you could.

By all means, type however you want to type, but if you never ever make a mistake, then you could push yourself harder.

Dunno about that. I type pretty fast (don't have exact numbers to back that up, just other people's comments) But regardless of that, typing two characters that are on opposite sides of the keyboard and each use a separate hand is, for me, pretty much error free. I make mistakes when letters are closer and using the same hand.

I don't think this is really accurate.

In my experience, the primary factor limiting my typing speed is the rate of errors. It's generally around 1-2%, but the time noticing and fixing those errors takes a disproportionate amount of time.

In other words, to type fast, learn to type accurately and gradually speed up while maintaining your accuracy.

I've never typed "sl" either. I have accidentally typed "l" and hit enter only to be surprised that it's aliased to "ls -CF".