I used to fully charge my cordless tool batteries for storage but since I got a new e-bike that sits most of the winter here I use the charging recommendation from the e-bike for my cordless tools as well.
1. Before storage make sure that the battery is not charged
more than 50% so that it will accept a periodic charge.
(You cannot periodically charge a fully charged battery)
2. Once every month you must attach the supplied battery charger and charge for a period of no more than 15 minutes.
3. Continue this procedure once a month until more frequent riding.
This process will make sure that your battery does not stay at a specific rate of charge for long periods of time.