Very very nicely written. As someone who suffers from sleep apnea and is incredibly curious about sleep this was a fantastic read. I would say one thing I am not sure you pointed out because I skimmed the apendix part is sleep quality. If you have poor sleep quality you will sleep more and feel tired, thinking you need more sleep. If you have good sleep quality you can get by with less sleep or more variance in your schedule. If you have sleep apnea you are looking at heart disease -> death if you don't sort out your sleep hygeine.