Importance of warm up. I hope this helps someone

I was checking a cassette I had made last month back to the original CD source for comparison. All my equipment had been on for 4-5 hours except CD player. I cued both up and the CD player was overly clear (bright) compared to the cassette made from the same source a month earlier. I thought well since this is a cassette I should expect some roll off in the highs after a period of time but not so soon. OK everybody. Im a cassette fan. I grew up with it and I know other mediums maybe are better. OK back to the warmup. I decided to let CD player warm up for 30 mins. I compared again and cassette was a perfect copy of the CD!!!. I can only figure the CD player was not warmed up. Everything else stayed ther same and was constant. I pay more attention to warmup now. I know it was important but I did not see how much until today.