Hi Kuri, I have had my bike for around 10 months now, and the health is still sometimes at 100%. When I got my Giant the battery health was at 99% and I've seen it fluctuate between 96 and 100.I usually try to charge to around 80% and the health tends to drift downward but jumps back up whenever I do a full charge. Also, while batteries will last longer if you can prevent them from frequently dropping below 20%, Giant actually recommends that you do just that every 3 months, see copy from their user manual below. I've only taken it down to less than 3% one time, and after charging it to full immediately after that, the battery health was at 100%.
If only 3% of the EnergyPak power is left, the Energy-
Pak will automatically switch assistance to ECO
mode in order to save energy.
If only 1% of the EnergyPak power is left, assistance
will automatically stop. Power assist level indication
bar will blink 3 times. Lights can still be used for
approximately 2 hours.
Power in the EnergyPak can be checked by pushing
the Energy Level check button.
Discharge the EnergyPak completely by riding the
bicycle after 15 normal charges or at least every 3
months totally before charging the EnergyPak again.
This will increase the lifespan of the EnergyPak.
When an EnergyPak is connected to the bike, some
power will get lost in the system when the bike is not in use.
To prevent this, EnergyPak can be disconnected
from the bike when not in use for more than a few days.