I bought an iPhone 4S two months ago. In the last couple of days I've perceived an average battery life of 12 to 18 hours with a light usage of the phone throughout the day.
I've followed every tip for battery preservation such as turning off Location services, I don't use Siri, I only download e-mails manually to the phone (no push or notifications), I set the auto brightness on, I try to keep only a few important applications running in background.
I would like to visit my carrier's technicians in order to get a replacement, but I would prefer to run some tests first to make sure that something's wrong with the battery.
Any suggestions?