I think you've been hearing either misinformation, information from people who really don't know what they're doing with their phone, or from people who constantly have poor signal. I have all location settings enabled all the time, I use 4G/3G all the time (which uses more battery than WiFi), I either have the display set on automatic brightness or close to max because I'm outside a lot, and I use my phone all throughout the day. I can't stand haptic feedback, so I have that off, but I do have my phone on vibrate only most of the time (which can impact battery life if you get a lot of calls/texts). I have no problem making it through 8 hours. There's nothing that I feel the need to turn off that I regularly use throughout the day. The only time I'll do that is if it's evening and I'm out away from a charger.