I don't believe in this end-all idea, actually, that only age can confer wisdom or supply the appropriate musicality for certain works. Schubert, Mozart, Mendelssohn and others wrote great, mature works when they were teenagers, that disprove the theory immediately!
Also there is another element, of a certain evolution in culture, (please be patient to see how I mean this!), of a sort of common source of humanity's knowledge and culture. Busoni once commented, I am sorry I cannot find where and must paraphrase, that the eletrical experiments of Edison, which were genius at the time, were now executed with the greatest frivolity by young boys around the world. That knowledge became absorbed into the greater human source, and became available to all.
So it is with culture, I believe; that is why you see so many pianists now who fancy themselves conductors. Difficult pieces will always be difficult, but certain difficulties we as humanity can overcome, and pass on from generation to generation. It was even said by Liszt's pupil Friedheim, that Liszt didn't have the greatest technical tools of all! That is not counting the sheer force of his personality of course. But at the time what Liszt achieved was unheard of, and would have taken anyone else years, if not decades, of practice (ie, maturity and age and experience). According to Friedheim, Liszt was surpassed in many ways by pianists of the next generations. And now, our knowldge of the mechanics of piano playing has become so scientific that it can be easily transmuted from teacher to student.
When we hear the recordings of Schnabel, of Serkin, of Richter, of whoever recorded the late Beethoven sonatas, we don't necessarily copy them, but a certain amount of the work in udnerstanding them has already been done for us. It is up to us to take this point into a new direction, to understand the pieces in terms of our times and epoch. In that sense, the idea of certain music requiring a certain age is really null.
Walter Ramsey