My general tipp for storing any lithium based battery (lithium ion or lithium polymer) would be to never store them completly full or empty. The chemistry inside those batteries is most "stressed" when holding maximum voltage and beeing like this will degrade the maximum capacity of those cells over time. That's why you shouldn't leave your laptop or phone plugged in and at 100% battery for a long time, it slowly degrades the battery.
I'm doing fpv flying as a hobby and I'll only charge my LiPo batteries directly before flying and I'll use a special storage program on my charger if I leave them on the shelf for a couple of days or weeks. For reference: A Li-Po cell is considered full, once it reaches 4,2 volts, it's considered empty once it dips down to 3,7 volts sustained, not under load (you can go lower under load, not go under 3,3 and after recovering it should be back up to 3,7). My charger considers 3,8 volts per cell a "storage charge".
Applying these principles to my V-mount, Sony BP-U and Canon batteries, I rarely charge them after using them and will just leave them at 1-2 out of 4 or 5 battery bars for storage. Not completly empty but definitly not fully charged. Then the day before my next shoot or prepday I'll charge them all up. I know this is not really as convenient as having them charged on the shelf but they will thank you this in how long you are gonna be able to use them at their max potential. If you are using them in 2 or 3 days anyway, go ahead, charge them fully. I'm from Germany, winter time is usually pretty slow as far as work goes for me, so I'll make sure are not full when sitting on the shelf for 3 weeks.
And a last thing: DJI batteries have a setting that allows them to slowly discharge over time after a certain day threshold. Maybe your batteries have a similiar protection built in.
Thanks for reading my battery health and safety guide