10 days at full charge would be really bad for the battery, and that's why DJI's auto-discharge failsafe kicks in way before that (it starts at 24 hours). The batteries are designed to cycle hundreds of times, and lithium batteries are actually the happiest if your charging is done in the mid-range of it's capacity. For example it's way better for a battery to be charged continuously between 20% and 80% than it is for it to be run down to 0% or charged to 100%. A balanced storage charge is right in the range of where a LiPo is happiest, as you would be charging it from about 20-40% (when you should be landing your drone) to 50-60% in most cases (for storage longer than a day or so).
A typical/ideal scenario would be to charge your batteries (currently sitting at a storage charge) up to 100% within a few hours of your planned flight time, within reason of course. They will charge nice and fast because they will already be sitting around 50-60% charge. When you're done flying, you will have, say, 3 batteries with 30% charge left. When you get home, throw them on the charger for a balanced storage charge and they will be in the best possible state until you're ready to use them again. That charge from 30% to 60% or whatever they stop at for storage is an ideal scenario for a LiPo.
You also wouldn't be discharging very often unless you charged up a battery and ended up not using it. Most of the time you are simply bringing the charge up from 20-40% (the level after flying) to 50-60% to be left at an ideal voltage for storage, so there isn't a lot going on there anyway. That's very easy on the battery, and what it's happiest doing.
Cycling the batteries from 0% to 100% or leaving them at or near 100% is far worse for longevity. Leaving them at too low of a charge for any length of time is also really bad for them.
Another thing you can do if you're worried about battery longevity is not charge them at their maximum rate if you aren't in a hurry, and they will last longer. With
M3P batteries being so cheap though, one could certainly argue it's not worth it getting overly concerned about it.