When I have used my bike gps for following a route all day, my doohicky could go a good three days before needing charging - but I specifically have it operating at the most basic settings, ie not talking to my phone, using less bright screen setting, following a preset gpx route (so not calculating a route).

I've had a battery bank that could charge it at least a few times, and battery banks seem to be the best bang for the buck for recharging.
Prices have gone down, and the last one I bought , I think a 10,000 milliamp one, recharges much much faster than older ones we have had in the family. I would have to look up the specs again, but the new one (which is a lot smaller and lighter than the older ones also) charges fully in 2 hours tops, whereas my old one took something like 6 or 8 hrs

a generator hub would be nice, but they mean a lot more money involved, whereas its pretty easy to have multiple battery banks at reasonable prices now, that charge fast and come in all kinds of millamp sizes, 5000, 10000, 20000.
Basically you look at the millamp size of your doohickys battery, lets say 3000ma and a 10,000 bank will charge it three times more or less.

so not that hard to keep using ones devices, especially with access to plugs usually during a day or at a campground or whatever.

and thats not even touching on the newer solar supplemented gps units out there, and which will certainly improve and improve.