[ayumisrael]

I highly disagree.
I don't think that time affects quality unless if it's really harshing the artist.

ayu and kumi released like crazy were their musical eras determined by a lot as the best.

"ayu's best musical era was around 2000-2002" and even started to compose where she released like crazy and kumi around ~12 single collection~.

Even now ayu really slowed down and some say that the music isn't like it used to be (when she released a lot).

Therefore I don't think that time is really a factor for making good music or not unless if the artist is really stressed for like making something big in a few hours.