Do all CD players benefit from burn in?

Having just finished my system (added cables) I wondered this. I use my wife as a guinea pig as she has better hearing and no idea what stuff costs. We both have found that any a/b comparisons suffer greatly after a few days (maybe less) and we are unable to tell any difference. Mind this is differences in specific samples we selected to test. I'm gonna stay out of this fight but I'm curious if folks do anything different for long term comparos than they would short?

Short answer is yes, I just reached about 500hrs on an Oppo 95 and witnessed it first hand!

During and after burn in, I find it helpful to leave the players power switch on.

sometimes a piece of equipment sounds worse over time, i.e., it gets bright and aanalytical and it sounds better , out of the box than after 500 hours.

Buconero, I had my SACD player upgraded and when I played it It sounded dull and dark. After a 100 hours it opened up. The new tubes had to burn in as well. Mike