Sounds like you're the right person to be commenting on this. My understanding is there is no real issue with battery longevity as far as deep cycling, and that keeping the batteries between 30-60 is fine for storage. But with some other electronic devices, I understand that the battery level calibration may get "off" and I've heard best practice is to do an occasional run-down and recharge. I think that's what you're referring to above. Not that it's an issue with the health of the battery, but just with making sure the electronics know accurately what the charge level is. Is this true for our DJI batteries as well?
I agree with everything you've said here, yep. 30-60% would be fine. Lipo nominal voltage is 3.7v per cell and they like to be stored at nominal at 25°C, if we're being picky. But they'll handle a range as stated without adverse effects.
What does hurt them is being fully discharged for long periods of time (though this is still not the end of the world), but what really seems to kill them is being left full. They really don't like that!
What's the best way to handle charging when you fly every 2-7 days depending on weather, wind, etc.? I have been fully charging them after each flight and letting them sit until the next flight. Should I not charge until I'm sure I'm going again. That would be kind of a pain in the butt, but if it made a big difference I would do it.
Well, perhaps just don't charge them until you're ready to fly. Ideally you store them at 60%,but if you're regularly flying every 2 to 7 days (like me, really) then the best compromise might be to charge them before you fly rather than after you fly. Yeah, don't leave them empty if you flew to 10% remaining or so, but if you're like me, after a flight you have between 25% and 70% remaining, which is far better to be left at than being fully charged and left at 100% for most of their lives, only discharging briefly during that weekly flight before copping a full charge again.
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Bottom line, compromise might be the way to go given we don't have a convenient Storage charge option like I do for all my other lithium batteries. The best compromise would be one that we're actually going to stick to and one that doesn't leave the batteries always full.
So, the best policy might be to charge before a flight rather than after a flight. That probably is the answer to most situations here, I reckon.
(Quick edit to add, don't forget about the controller! It's also lipo powered I believe, so it wants to be kept 30-60% ideally. Charge before you fly and do the controller only when the leds are showing one or two before a single flight, perhaps. Fully charge it if you're going to fly all your batteries, I guess. It also can be used to charge your phone while it's on, so that might be a convenient way to discharge it a bit)
*all of the above is based on my experience and knowledge as an electronics hobbyist who also does relatively basic electronics repairs in a small business as part of a greater service (fix the thing so it can be accessed in order to do the job). I don't have formal training with battery technology but do have years of experience working with lipo, li-ion, nimh, nicad and Pb battery chemistries. The advice here is my best guess rather than engineering fact, so please use your best judgement!