Lets take a look at the breakdown.
|Goal (100 hours)||2.25||2.25|
I haven’t even looked at the microcontroller current consumption and optimization yet. I’ve been debating my choice of microcontroller, but it’s hard to know what is marketing and what is actually achievable. However I've been debating eliminating the regulator. Rather than using a reference voltage I could go back to my old voltage divider design and then everything is ratio metric. As the battery voltage drops so does the reference voltage. This would simplify things potentially. Switch to the Atmega 328 or the nRF51422 which is my preferred goal.
Looks like the measured does line up with consumption. I removed the bridge connections and consumption dropped to 15 - 17 ma. This is still quite high, but this is no optimization and running the ADC and Instrumentation Amp at full tilt. So the bridge is pulling similar power as everything else.