Assuming I've read your schematics for the Mark II correctly, it appears you are using an LM555C (instead of LMC555) and it is your main power hog. Since the LM555C uses something kind of around 5mA of supply current, this would suggest a battery life of around 120 hours (assuming 9V alkaline battery rated about 600mAh capacity) of use when the circuit is actively powered. Fortunately for you the 555 comes in a CMOS flavor which has dramatically lower power consumption, is pin compatible, and is otherwise quite similar to the bipolar LM555C. The LMC555 has a typical current consumption more on the order of 120uA.
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