The reason most people's batteries don't last long is that they buy a battery which is just enough for the range of their commute. I suggest buying the biggest battery you can afford so that you don't have to discharge it so much before recharging.
With the Li-ion batteries in cars it's not the amount of charge cycles but the portion of the battery that is used.
If you charge from say 40-60% each time it will last longer than a battery charged from 80-100% or 0-20%. So keeping the charge and discharge zone in the middle of the batteries voltage range (rather than at each extreme) will give you the best life for the battery.
I'm gonna assume that an ebike Li-ion works in the same way as a car battery.