If you know you will not be using your battery for a few months then it is wise to take some extra precautions: The rate at which a lithium battery self-discharges (goes flat) is highest when fully charged and lowest when almost flat. So over a long time your battery will loose capacity least by being partly discharged. However almost flattening a battery we know is a bad thing to do.
A compromise that reduces the loss of capacity over time, yet still preserves the battery, is to store it at about 80% charge. You can estimate this by riding your e-bike for about 20% of the normal full-charge time or distance.
It's best then to store the battery in the coldest convenient place you can find and then, if possible, give short charges every 5 to 10 weeks.