Where did you hear this?
But what I gather from your responses is that this was the exception rather than the rule even at those times?
Back then concerts where a different deal as to what they are today. Back then there was no recordings to listen to on your CD player so the only time people really got to listen to music was at concerts, so naturally they where longer than nowadays.
I don't think that the possibility to listen to music on a CD player would lead to fewer people attending concerts. And even if it were so, the natural consequence would be to have more, rather than longer recitals. No?