Rather than looking at the bars, you can change the display of the 'signal strength' to read in real numbers.
While at the home screen (ribbon), hold down the half moon key while you type NMLL. The bars should change to read numbers. For the 'signal strength', if you are in the 100 area (that means -100 dBm), you will be transmitting at maximum power (2 Watts), and since coverage is hit and miss at this weak a signal, you may end up transmitting many times before the packets make it through. This might help explain any poorer than normal battery life. I consider anything at -90 to -50 excellent.
To get the bars back: While at the home screen (ribbon), hold down the half moon key while you type NMLL again.
they have all kinds of tips and tricks, hope this helps =)