I am sure that we have all beeen there where we wroted code that worked and was accepted. Then weeks or months later we thought that something outside our code could cause problems in a very rare case and wanted to correct out code to cover that rare occurane. Managements resposne was do not make the change, it will cost too much time and money.
Then months later the rare occurance happened and was going to cost much more in time and money to fix than an earlier fix. The fail to remember that they were warned. Then you were asked why you did not catch the potential problem.