Incipient VRS was demonstrated to me and I found it was very easy to get out of. I was told and left to believe that, like low RRPM, if left unchecked you will die, simples.
I have no reason to question the wisdom of my instructor on this matter. I'd imaging fully developed VRS in training does cause wear and tear on your machine and carries unnecessary risk - thanks Hughes500 for sharing your story, incipient VRS is as far as I would ever want to go.