That is not just conventional wisodm that is the standard for IDe cables that they are to be 18" or less. longer cables do not meet the standard. whether or not people have problems with using longer than standard cables depends alot on the quality of the cables they buy. I have seldom seen anyone who uses the longer cables have a problem if they used good quality cables. on the other hand I have seen people who boght the cheapo generic cables and have plenty of problems.