True but picking up a guitar around the house and playing with a band are 2 different beasts. You can practice 8 hours a day by yourself and still feel sluggish with the band. Still no excuse though, I guess they somehow could've still rehearsed with just the 3 of them to stay in shape.
Edit: Someone might've mentioned this before but for Robert and perhaps all of them, no one knew how long it would last so maybe it was balls out all the time. I guess by 72 maybe they should've known they would be around for awhile. Robert did mention lots of times about tea, lemon and honey, maybe that was the extent of knowledge of vocal care back then. Like put a hat on or you'll catch a cold, viruses don't care about hats.