That's exactly it. If you're at work or school all day, and you're actually working or paying attention in class and NOT playing with your phone, you should be okay with battery life, even with normal usage (a few texts, calls, emails).I remember when the % became available to everyone, a fair number of us began obsessing over it. Just relax and enjoy your use of the phone. I'd recommend only becoming concerned when you can't get through your normal day without needing to put the phone on the charger then it will be the time to review your habits and settings.
I usually get through the day with mine with more than average use, I do charge it once a night though. What sort of battery percentages are you getting throughout the day?I was just wondering, how long should the iPhone 4's battery last? I can usually get through a day on mine, and I have done ALL of those battery saving tips, setting time zone, fetch email, half brightness, etc. is that normal?