I may have found an answer to my question. My battery life is back over 24 hours. Investigation suggested that it was syncing-related. I tried the following two things (after other failed attempts) based on the weak evidence I had:

1. Set my phone to always keep wi-fi on during sleep (under Wi-Fi, under Advanced in the menu). I have weak cellular coverage in my house, so falling back to cellular isn’t necessarily better for battery.
2. Disable Currents from syncing. It is a heavy abuser, and I don’t use it.

Problem solved.

By the way, two apps I have used for keeping an eye on battery are BetterBatteryStats (good for investigation) and Battery Widget? Reborn! Pro (general purpose, good for keeping an eye on drain).