Welcome to the forums Chuck!
Battery life is different for every device, but in general it should last at least a couple of days on a full charge - and yes, turning off the wireless radio will greatly increase battery life.
As for the memory issue, the problem with ppc's in general is that the OS does not really close programs, it just minimizes them to the background, in case you should need them again. What I've heard is that the OS is supposed to close the programs and allot memory as needed, but that never seems to be the case.
Long explanation short, most people install a third-party memory/task manager -
Magicbutton is free, and a lot of people seem to like it. Here is the developer's
page.
Hope I've answered some of your questions - good luck with your ipaq!