[T-Mobile myTouch 4G Slide] Blue6IX:
Well, firstly, good call on the anker batteries. I have one, and it's changed my life with this device. I went from being exactly as you described (scared to go somewhere without knowing exactly where my next source of power was) to not paying it much mind.

Secondly, if you are unrooted stock - then you have a whole lot of apps working in the background and conspiring together to drain your battery. ...and there's nothing you can do about it because both T-Mobile and HTC saw fit to place them there, running around the clock and beyond your control.

This is known as bloat, and on this phone it's beyond out of control. It's out of control on other phones, but they took it to a special place of exasperation on this one.

I am not sure about this 2x battery app you're speaking of, i've never used it. Consider this, though, it's one MORE app running on your device and draining your battery - and if you are stock this may be something you can ill afford.

As far as the wifi/data dance, this is nothing more then a feel-good measure that really isn't doing anything for you except adding to your interaction with the device. The time your screen is on to make that change takes more battery use then you would save on several hours of having one or the other switched off.

Check this link below (another XDA post):

Everything you wanted to know about Li-Ion batteries but were afraid to ask!

...and it may help you out with battery care.

For me, running my custom ROM with an anker battery and all the apps/widgets I prefer to use I can get 6-8 hours out of a charge on the anker battery with semi-steady usage.

This is with both wifi, mobile data and background data on, and the screen on but at mostly dim brightness for 4-5 of those 6-8.

If I overclock the processor to 1.7Ghz (stock it stops at 1.2Ghz) and hook it up to a television using a playstation (game console) emulator...running flat out at full speed I can drain the (anker) battery in as little as 3 hours.

Something that may interest you as time wears on and you get used to having the anker batteries and using them is what is mentioned in this thread:

external battery pack! Awesome!

...and there are many out there and good deals to be had on some, poke around a bit and you'll find one suitable if such is your desire.

One last thing to consider - make sure you are using the proper charging port.

Most USB ports on computers only push half an amp, as well as nearly every single secondary port on chargers (think car chargers with an 'extra' USB port). Half an amp is not enough current to charge the device if being used, and barely enough to see positive battery increase if not.

Make sure whatever you plug into is pushing 5volts 1amp, or you'll see your battery level continue to drop as you are charging.

(oh, and GPS is something you WILL see more battery life from turning off if not using - so having something like a soundhound app widget on your home screen with location on will eat your battery before you know it's gone by activating the GPS.)

Dimming the screen if possible will see you the greatest gains in battery life, and then getting rid of any apps you can that are running in the background is the next biggest step - but again, if stock and unrooted there is only so much you can do on app management.

DON'T USE TASK KILLERS - EVER. (they do much, much more harm then any falsely perceived good you may think you are getting from them.)

Recap:

Screen = biggest battery drain.

GPS chip/use = second biggest drain.

Apps in background = third biggest drain.

Wifi/mobile data = negligable drain.

Hope this helps a bit.

Edit:

Oh, and welcome to XDA!