My Indulge always runs fast and smooth and I've extended the average battery life from 6-8hrs to 12-16hrs without the need for charging. (it depends on how much I'm on the net)
First off, if you're not using it...shut it off. Pull down the top menu and shut off Wi-Fi, Bluetooth and GPS.
Go to your apps and find "Task Manager". Tap the "RAM manager" tab at the top and then click both "Level 1" & "Level 2" and then hit "Clear memory". I do this every time I'm done doing something and I'm about to put my phone down or away for an extended period of time.
Then go to "Settings > Accounts & sync" and shut off "Background Data", unless you're truly in love with constant email, Facebook, and whatnot updates; you can do all that shi....stuff manually.
The coup de grace is the "Any Cut" app. Go to the Android Market (you'll have to turn your Background Data back on for this) and download the "Any Cut" app. Once it's installed make a shortcut for the "LTE Function Test". Open the shortcut and hit "TURN OFF". Now you've shut off your 4G. It'll turn itself back on every time you make or receive a phone call, so you'll have to turn it back off again.
If you do all of this, your phone should run a lot smoother and quicker and you should save a lot on battery life.
PEACE!!!