[carpetmojo]

I use mine a fair bit, and I'm almost sorry to say, comparing our experiences, my T1 battery seems awesome , miles better that my 650.
I only wall-charge, on usually two bars, definitely as soon as down to one. I never switch it off, always use Sleep Mode.
If you are using the PC to download etc.. it shouldn't have any effect, that only happens - unless it's a dud battery - if it's left to do a full charge on a computer, and then not often, but it can fully discharge it overnight, for example.
You cannot overcharge it, so wall-charge it overnight, give it a good blast.
And - silly I know, I'm sure you're right - but are you sure the wi-fi is off ? ie not ticked, and the "close wifi down" is ticked ?