Mmmm! Good practice or not i have been for Years ,both here and in Penrith Running my Air Cons well below that mark,and so far nothing has happened to any of the Units we have had!
In Penrith where it sometimes reached up to the 40 Degree mark,i always had my setting on about /2122 and that ran most all day.
Here last Week when we got those 36 Temps i was running it at 19/21 sometimes lower and so far all seems AOK.
I like to feel the Cool Air not just the Room being kept sort of a level Temp.
But we all have out likes and ways I guess,
Cheers