When I charge up to go flying the next, but something comes up and can't go play, my batteries self discharge after 3 days.
The self discharge drops the battery to approx. 50% for storage. If it were me, I wouild get them close to 50 percent, say 45/55 %, if the self discharge stops at 50%, I would use that as the target.
I have the Mavic Gen I, but the same procedure can be used for any LIPO battery. Never store full, never store empty, go for 50%...
30% is okay if you're only storing your batteries for short periods of time. See these tips if storing batteries for longer periods of time.So I deplete my batteries to around 30% and they are on a 5-day discharge period.