@ZamZiBam
"If you overburn a CD-Rom, it can have varied lenght!? Correct?! "
Yes, it can.
But in fact, all CD-R or CD-RW manufactured from the same stamper will have the same behaviour. It's build-in, from the techno (there can be some trouble in metalization, but you 'll be very unlucky). If you take a x CD box, then overburn the x CD until it failed, you have a very very good chance to have the same length for all the x CDs.
And a stamper is used for many many CD-R/W - they're expensive
. So length is not as random as you expect