Their are so many (many) variables that your original post is lacking that can help determine if this is usual or unusual.
For example:
-Are you jailbroken, if yes, what apps have you installed.
-Do you have "Push" email set ON (also, how many emails accounts do you have set up).
-Do you have "Push Notifications" set to ON.
-Do you have "Location Services" set to ON.
-Are you streaming you media or is it saved locally.
-Whats you screen brightness set to.
-Do you live in an area of good or bad reception. having a weaker signal (low bars) means your phone has to work harder to maintain that connection causing you to loose battery.
-Are you playing graphic intense games.
-Are you on 3G or EDGE, and how often are you on WiFi.
I don't know what normal is, but the average from what I've seen here on the forum have been between 5-7hrs of various usage patterns.