My scrub script:

    dd if=$1 of=/dev/null iflag=direct bs=16M status="progress"
    smartctl -a $1

If someone wants to properly study SSD data-retention they could encrypt the drive using plain dm-crypt and fill the encrypted volume with zeroes and check at some time point afterwards to see if there are any non-zero blocks. This is an accessible way (no programming involved) to let you write random data to the SSD and save it without actually saving the entire thing - just the key. It will also ensure maximum variance in charge levels of all the cells. Will also prevent the SSD from potentially playing tricks such as compression.