Ok, so all bits have to be rotated, even when powered on, to not loose their state?

Edit: found this below: "Powering the SSD on isn't enough. You need to read every bit occasionally in order to recharge the cell."

Hm, so does the firmware have a "read bits to refersh them" logic?

Kind of. It's "read and write back" logic, and also "relocate from a flaky block to a less flaky block" logic, and a whole bunch of other things.

NAND flash is freakishly unreliable, and it's up to the controller to keep this fact concealed from the rest of the system.