Running the battery down to 30% regularly is not okay. You should be recharging at the 50% point for maximum battery life. 40% is okay if you must, but try to catch it before that. If you need more time between charges than that, carry a charged spare battery and exchange them when the one in the phone gets down to 50%. (Properly batteries last for years, improperly cared for batteries can die in 6 months.)