I do not feel that artists have to spend hours a day to keep their technic efficient. If that were the case one would not be in a position to participate in the other joys of life. Nor could he enrich his art. Of course, mind you I am not saying that one should not work. But definitely I say that if one has developed a firm technic, it is not necessary to slave over the instrument for the rest of his life in order to keep in good form.