Older folks mastering music - are they hearing everything?

I should perhaps add that I'm not a mastering engineer, merely a musician with a great love for good sounding music.

 

On a side note, I'm a bit puzzled by the urge to use "flat transfers" of old tapes, when we all know that they will deteriorate with time. Newly released remasters that are supposely flat transfers often sound rather dull to me.