This is an example so can load HUGE address-lists. I prepare them on a Linux system with a script. Then I download them in files with schedule.
http://forum.mikrotik.com/t/large-blacklists-for-firewall/136869/3
It will not overwrite any existing addresses.
The stated time is the longest possible time in ROS.
This format is made to have small files and so the easier to transfer.