Assuming eight hours of sleep are part of staying healthy, sixteen hours a day really is the most you have.
And as great as it may be to fantasize about having more hours in a day, it’s not going to happen. You have to make peace with the fact that sixteen hours a day is the hard cap. And for most people, spending all those sixteen hours productively will end in a burnout. Not to mention it’s common to have around eight hours of work, and a varying amount of mandatory activities that are part of life: shopping, eating, cleaning.
So that leaves us with less than eight hours on an average workday. Probably around five or six, maybe less though. That sounds… kind of depressing actually. You may want to spend that “leftover” time on cool productive things, but chances are the eight hours of work have already gotten your energy way down. Even then, you still want some time to relax and do something not intensive, so that just cuts it all up even further.
Guess that leaves no choice but to bank everything on the weekends?