Banjos certainly mellow with age. I have an english banjo made in 1923 with the name "melody Joe" on it. Its tone is very mellow and great for song accompiament. My more modern Gold tone (about 3 years old) still has some way to go but its getting there. I once had an old Deering with a cast metal body. This was very crisp and was OK for Bluegrass but obviously hadn't mellowed. Obviously a lot depends on how its played, but this is just the same for guitars.