it's depend to tho load, as I thik
let see: U=R*I, where U=12V supplied from the battery, and R is the resistance of the Load supplied by the battery.
the current is given by: I=U/R.
The power of battery is 55mAH
no of hours of a static load, with a Z impedance is = mAh/mA, whare mA is the current truth the load,
so, Time= 0.055/I (I in Amper)