Use it with light set at medium, and be careful when setting it high when need it to remember to lower light when you don't, and it will last for several hours of NOT intensive use.
WIFI? Best thing you can do is to get a car adapter, travel adapter, battery extender and any other kind of energy supply to keep it alive.
I've got all mentioned and power is no big deal now.
The batt extender I made it myself, but you can buy one. Take a walk on the forums and you'll find many providers.
You'll find how to make one yourself too.
It's easy to make, but maybe you'll be using it faster if you buy it and besides, you won't save one buck if you make it yourself... It's worth just for entertainment, IMHO.