Hi!
I was read some post and articles about li-poly batteries, drone batteries (mavic, phantom ect). Specially when you are not planning to fly in short future there was recommendation to keep batteries non fully charged but charged till 50%. So my question: is if you not planning fly one week or two do you charging your spark batteries till 50% or leaving discarged after last session around 25%-30% or you charging full and dont care? What is best in your opinion?

The Spark batteries are doing it for you. If not used they start decharging themselves after 10 days to the recommended level.

As far as I know low percentage storing is not recommended.

After 10 days they'll start discharging to 70%.

If i am not planning to fly "tomorrow", I would just store them at about 60-70%
Which is 3 LED on, about.
Like I store my older phones/phone batteries too (~70%).
Works so far.

It is recommended storing the battery on half of the power (50~65%) if you are going to leave if for a long period. And as Wachtberger mentioned, the battery will discharge itself. Please refer to the manual: