Batterie technology is fascinating and I expect big strides in the next 10 years (along with consumer generation of electricity)- to the point where people will be able to basically take their home “off grid” relatively easily.

I forget where I read this, but someone posited that the goal has always been “all day” battery. Ever since the first smartphones ,we’ve had, largely, the same battery life. It lasts most of the day and that’s good enough for most people. The secret, though, is that actually the batteries have gotten way bigger and more energy dense, it’s just that the processors and mobile radios are also more power intensive.

I suspect if you put a modern battery in a 5 yr old smartphone it would last 2+ days. But you’d have to deal with 3G radios, bad GPS, and slow performance.

Depending on what you’re doing 20+ hours is already doable pretty easily on an M1 MacBook. I’m a pretty intensive internet user and I still get 10-15 hours.