You should be cautious of that sort of self-evaluation. There's a sleep study that showed that people are very bad at evaluating how they are affected by not getting enough sleep.:

after just a few days, the four- and six-hour group reported that, yes, they were slightly sleepy. But they insisted they had adjusted to their new state. Even 14 days into the study, they said sleepiness was not affecting them. In fact, their performance had tanked. In other words, the sleep-deprived among us are lousy judges of our own sleep needs. We are not nearly as sharp as we think we are.

But, in that same study, the group that showed little or no cognitive decline slept for 8 hours, and I'm finding recommendations that say 7.5 hours is enough elsewhere, so I'm updating towards 7.5 hours of sleep and naps being all that's needed (as long as you have good sleep hygeine).

Thanks for indirectly prompting me to re-evaluate my sleep habits. I'm doing the same thing as you, basically (learning on my own), so it makes me very happy to discover that I could get more done each day!

I think you may have misread what I wrote. I pointed out in my original comment that, from what I've read, 7.5 hours seems to be not enough sleep. So it would follow that getting more sleep would increase performance. I know that excessive sleep also causes problems, but that's clearly not relevant here.