I own a P3P and I have two batterys for it.
I have read about people draining their batterys to 5% every so often to improve battery life or letting the batterys discharge over time and then charging them again.
Do these methods help improve battery lifespan?
I dont know what the best why to maintains batterys are so any suggestions on how to maintain batterys would be appreciated, thanks.

Drain them down to the point the battery will not power up the phantom. Do this about every 20 recharges. Set up your batteries to discharge after 3 days of being fully charged. This will discharge them to about 65%. Warm them batteries up to 70-75 degrees before you place them into the phantom just before flight. My batteries have been recharged 30+ times and still have 100% battery life.

mjlstudios@yaho Posted at 2016-2-20 18:52
Drain them down to the point the battery will not power up the phantom. Do this about every 20 recha ...

What he said + the full discharge-recharge cycle is for the "intelligent" part of the intelligent battery, not the cells themselves. Every so often (20 or so charges) it's good to perform the full discharge-recharge to allow the circuitry in the battery to know what near-zero percent is. You'll find you get more out of your battery charge if you do.

You don't have to do this too often, like the others have suggested, a full discharge-recharge for every 20 times is ok, it will help the battery adjust the percentage display on the app. When you notice there is large voltage difference of cells, you can try this to see if you can correct the display.