reason for 10-12 hrs being optimal?

[Shannon]

I say 10-12 hours is optimal because:

1. At the time, that was the best information I had to go on.
2. Most people cannot or will not use a program for more than that per day.
3. It prevents mental exhaustion.

Our intrepid explorers here have since shown pretty good evidence that the optimal range is actually more likely something like 12 to 21 hours a day, up to whatever limit you can handle without exhausting yourself during sustained usage.

This will change dramatically for 6G programming. I don't know yet what optimal usage patterns for 6G will be, but I will tell you this: It will likely be a LOT less time per day, and you'll need to take following the instructions a LOT more seriously than the majority of you currently do.