Believe me the stuff out there now can already do a lot for days if not weeks with contemporary HW / SW. Some things could be done "enough" for months or years without recharging even though very limited in what they're doing.

One doesn't need to stream 4k 60fps video and 192kb/s hi-fi stereo audio and so on continuously to be a relevant consideration for what your device could do given the instructions to do it.

You know you've got all sorts of things like wrist watches and battery powered medical / consumer devices and stuff where the batteries last months / years without recharging and the devices are still able to do stuff and sense stuff and wake up and do even more stuff whenever needed...