I think if you follow a short set of 'best practices' you will be just fine and your batteries will last a very long time with very little effort:
1) Never leave your batteries sitting with a low or zero charge any longer than you absolutely have to, that is probably the worst thing you can do for them.
2) Never run your batteries down to zero or close to zero (20-30% is when most people return to home)
3) After flying, charge your batteries up to the ideal storage level of 40-60% (2 solid lights, third flashing) ASAP
after they have cooled down. They are OK at this level for up to 3 months,
after which you should cycle them again. You don't want to wait a long time before charging them, especially if they have been run very low.
4) Never leave your batteries with a full charge unless you intend on using them shortly after - be especially careful not to leave them at 100% for long in very hot climates where it's more common for batteries to swell. The best time to use a battery is shortly after a full charge so you know all the voltages are ideal.
5) Don't not rely on the 10-day auto-discharge, think of that as a fail-safe rather than a convenience feature.
6) Keep an eye on battery voltage when flying (a menu option allows you to display the lowest voltage cell on your screen). If you ever see it drop to around 3.4V or lower, time to land ASAP. Below that I would consider it an emergency as the drone will shut off around 3.0V. Try to be on the ground before then
7) Be especially careful (or don't fly at all) in really cold weather - the batteries are not designed for that and can behave unpredictably. The
M2P is technically rated down to -10C. If you have to fly in really cold weather, keep the batteries warm in the car or next to your body until the moment before you need them, and come home early with plenty of battery percentage left. You can check the menu for the battery temperature - I wouldn't fly unless this is above 20C.
Like I said, not all these are necessarily firm rules, but they are best practice.
To answer your other questions:
- Storing a battery on the aircraft isn't a big deal IMO, but technically best practice would be to not do so. I do it when traveling to save space, but at home I take them out. Even better would be to keep the batteries in LiPo bags but it's up to you how far you want to go with that.
- Best way to achieve full charge on 3 batteries before flight is to put them on the charging hub and wait for them all to be charged
It will charge the
highest charge battery first (the idea being to get you in the air faster), and it charges sequentially not simultaneously.