All CD machines are different , some seem to take longer to run in than others . The Ayre  C5 I purchased  last year , new , only took about two hours to sound it's best , to my ears , yet the manual says 100 to 500 hours . The sound for that first few hours was unlistenable , even the dog beat it .

I never thought this was necessary until I just got a NAD CD player that sounded dry and lifeless right out of the box... A good 40 hrs. until t was listenable... Go figure...