That’s… more than a year

They already have in many ways

Let’s reframe the question:

How long could our devices last on a single charge if that didn’t do stuff like this?

So “16.4 mph north” is sufficient.

No, it’s not. “North” is a two dimensional direction on the surface of the earth. But we live, and can throw babies, in three dimension. Therefore you need to specify the inclination as well. “56 furlongs per minute, north, 0.3 radians” would suffice.