Everybody should get BatteryDetective from Cydia. I just mentioned it in another thread, but I'm just a user - not making any money off of this...
In my opinion, it is the best tool available to try to determine if your phone is draining too quickly, and also to quickly tell when you've finally found the culprit.
If you open the app and select "Battery Info", you can see a lot of information on one screen. Some of the important ones are:
MaxCapacity: Displays how much energy your battery is acutally capable of storing.
DesignCapacity: Displays how much energy your battery was designed to store. Use it to reference MaxCapacity to see how much your battery has degraded.
CycleCount: How many times your battery has fully charged. This isn't how many times you've plugged it in, it's how many times you've charged 100% of the battery. For example, charging it ten times from 90% to 100% would count as 1 cycle.
Drain: This is the big one. This tells you exactly how fast your battery is being drained. It updates every 20 seconds or so.
For the 4S, the designed capacity is 1430milliamps/hour. If you are seeing -143mA, the phone would be drained in 10 hours. You can leave this page displayed and put your phone to sleep. Let it sleep for a minute or so, and then quickly unlock the phone and check your "sleep" current drain. On my 4S, that drain is usually between 4 to 8 mA. When I've had problems, like when iTunes Match is misbehaving, I've seen that number rise to 450mA while asleep and the phone really starts warming up. It is drawing 100x the amount of current that it should be.
With this app, it's really easy to make changes and see actual before-and-after results from your tweaking instead of relying on how it "feels".