> At times 18 hours a day
I hope you're not still doing this, it's nothing to brag about.
As long as you do it because you want to and not because you're forced to for work or something who cares? Whatever gives people energy
Sleep deprivation does not give you energy.
I do personally find myself most productive with a cycle of 20 hours awake / 12 hours asleep. Circadian rhythms vary by person.
Unfortunately, the world makes it hard to keep that cycle, and so instead I mostly do 17 hours awake / 7 asleep, which makes me feel constantly tired (though less tired than 16/8 at least).