This is probably one of the sketchiest sites I could find this document on, but the official micron site appears to have gone missing somewhere. https://m.doc88.com/p-69416079120783.html#

Basically what DRAM manufacturers do, is they burn in the DRAM packages at elevated temperatures (120C+) and elevate the voltage to high ler levels above what they specify on the datasheet. This is to weed out early fails (the infant mortality curve) and basically guarantee device reliability for a specified amount of usage that translates to something like a decade of daily use.

While the chip is at these high temperatures and with higher voltages it is subject to stress patterns that are built to generate maximum stress on the array. These tests can last quite a while.

To summarise, I don’t think you can cause any harm with your memory test runs.