Years ago when I got my first mobile phone I had battery issues. As soon as I got home or to a destination I had to charge the phone. Today that's all behind us. My phone can last several days between charges.
I have had less luck with mobile computing devices. I have a small (7 inch screen) tablet computer running Android that I can run off batteries for a prolonged period (likewise with TI-83 and TI-86 calculators running TI-BASIC) but I've had issues with all larger devices. I have a large (10 inch screen) tablet computer running Windows 7, a netbook running Linux, a netbook running Windows XP, and an ibook running MAC OS X Tiger/unix none of which have adequate battery life. As a result I typically run all of these plugged into the mains/wall outlet (and this lets me turn up the screen brightness to something closer to what I get from my desktop computers). Fortunately, I seldom go somewhere where I don't have access to a mains electrical supply. (An inverter works in the car.) It's my impression that the majority of the time people run their laptops off the mains.
The smaller mobile computers have inadequate computing power. The larger mobile computers have inadequate electrical power. As a result I currently tend to favor a netbook or small laptop for mobile use. (They also have a reasonable screen size and a real keyboard. see my 8 Feb. 2012 post. They are lighter to lug around than my physics books.) Perhaps I should/could attach 2 or 3 more batteries in parallel to my Acer Windows XP based netbook. That might be just about what I'd really want. Perhaps laptops should come with a larger battery option. (Just like they may now come with different storage options.) I know of at least one laptop that offers this but it was only a choice of a 9 cell battery pack versus a 6 cell battery pack.