@Boots33 I haven't done a writeup of mine, perhaps I should fish it out of the pool sometime and get some photos.
The DS18B20 has a tiny standby current, something like 750nA. Even with 30 second poll intervals, I'm finding my sensors typically get near-shelf life from the batteries.
The physical setup is pretty basic - just a Pro Mini, battery, radio, and ds18b20. There's no circuitry for regulators, dc convertors or battery sensing. Of course I did remove the onboard regulator as it will draw power from the 'out' pin.
One thing I had to do was reprogram the fuses - you may find the Pro Mini comes with the BoD fuses set to like 2.7v. You can set it down to 1.8v so you'll get much longer life out of it. The effort is worth avoiding the hassle of more frequent battery changes.
Battery level sensing uses this VCC library: https://github.com/Yveaux/Arduino_Vcc