VDV was sold because he was struggling with personal issues, which was born out by the fact that he separated from his wife about 2 months after he left us. It was his last attempt to fix his personal life, we can't deny the guy that.
Re his stamina, his issue was not fitness, it was the fact that he ran his ass flat out, all the time, you can't train to be that kind of fit. He doesn't pace himself (a marathon runner may be able to 26 miles, but can't do so by running at top speed the whole way).
And if he gave us 60-70 minutes of class, it would have been fine to bring a sub on for last 15-20 minutes.