I have found that I need to replace my Treo 600 battery every 1-1/2 to 2 years, which is equivalent to the 500 or so charges that a lithium battery can take. The symptoms of a dying battery in this smartphone are:a) dropping cell phone calls as soon as they connectb) rapidly falling charge level throughout the dayc) incorrect signal strength readings - simultaneously displaying "no signal" while showing 4 bars.This battery has built-in overcharge protection (very important), installed easily, and came at a great price.The only thing it lacked were any instructions for how to disassemble the phone and install the battery, but I didn't need them since I had done it before.