The lower the amps you program, the lower the wattage the battery will use.
If you only use 35% of your battery capacity it should give you a very long life span. Of course all of this depends how far you travel on your bike before recharging it, and of course pedalling helps take stress off the motor to keep amps down a bit.
Set the controller to 10 amps and you should never see more than 500w being used by the motor when it is at full pulling power. Though you will sacrifice the torque/ pulling power of the motor with such a low amp setting.
A cycle analyst is what you need to figure out and monitor how many watt hours and amp hours you are using on a journey or per mile/kilometre. For instance one mile may use up 1.5 amp hours. If you have a 15ah battery that is 10% of its full capacity.
What type of battery and what voltage and AH have you got?