It's not like I came up with this myself. And most of them are marked so that the coach who plays for my auditions will remember what tempo we agreed on. He did it for himself. Other people just benefit from it.
BTW, do not call yourself an audition accompanist if you don't know the ballpark tempo (really there is not usually that much variation in the standard rep) of the standard audition arias. No one expects you to know the pieces no one has ever heard of but you should know the way the standards go. My book is marked pretty well but I am spoiled and sometimes forget that not everyone knows how the Flower Song goes (and if Carmen isn't standard opera, I don't know what is!).
Houndentenor
"Sometimes I wonder whether the world is being run by smart people who are putting us on or by imbeciles who really mean it." -- Mark Twain