Some of the stuff they get away with down here is mind-boggling to a guy from the frozen north that deals with clay based dirt.
This wall would last about five years in Montana. Taller walls with heavier loads that are close to the edge are common here and don't seem to move. In the early days of this city, there wasn't much regulation as to building specs. Now any retaining wall over four feet high needs to conform to a common engineered spec. So, I assume that this wall should last for at least as long as I'll need it.