From what I understand, it's about 10-15 years, give or take (and as you noted may depend on the amount of usage). What also should be noted is that the CD drive mechanism is usually made by a party other than the audio manufacturer and the period when such drives are produced will vary and will often be less than that 10 year period (especially considering that the CD player manufacturer will develop and test and have software related to that drive and that's why when a drive is no longer made, such as the BCD-1, they come out with a new model as it likely doesn't make economic sense to write software for a new drive and then back engineer how it will fit in an old model - an effort that manufacturers would rather put into a new player).
