When not using any of my quads and especially the DJI ones, I check my batts and charge them to storage voltages every 3 months. If you leave DJI batteries a long time they will go down so flat they may never work again, because them are smart batts and means the electronics draws a small amount of current even when off which sooner or later will kill the battery if you dont check them now and then.
So every 3 months I go through all my lipos and check and top up charge them if they need it.
Its a chore , but far cheaper than buying new batts and as dji drop making batteries for some models, it could get very hard to buy new.
I also find it a lot easier than using the dji battery chargers and waiting until roughly 3 leds are on to use seperate charge leads.
Below are the 3 types I have for DJI mavic air, DJI Mavic Pro and DJI Spark.
Some of these leads getting hard to find on the older models, used to be loads on ebay not so long back, but a lot harder to nail down now.
Only link I have at present is for the mavic air charge lead I got recently from ebay
You will also need a balance charger than you can turn off the balance mode or these leads wont work. I use a b6 mini which has this feature:-
Then I just set the charger to 3s charge to storage voltage for LiHv cells.
I do know that the DJI mavic air and Mavic Pro model smart batteries have electronics inside that auto discharge to storage volts after a certain amount of days, I just prefer to do it this way.
Sooner or later the batteries will not hold decent charge anymore, but if the electronics is kept alive, then there is at least the chance to change the cells if you have the skills and make sure you dont let batteries get to the point where there are no leds when charging as the battery chip inside will reset and no cheap easy way around reprograming these at present.
Dont forget to charge up rc controller aswell, but have to do that manually and I normally charge to around half the leds on.