The term defect aging in software testing is very common term not for Testers but usually for Software Test Leads, Test Managers and Project Managers. Defect aging is basically let these chaps know how long it has been the defect under question is not closed or still open and/or how many times the software defect life cycle is performed on that defect. The greater the number of software defect life cycles performed on any defect the greater the cost actually incurred on that defect, and this is the very alarming sign for any project and project team as well.
Defect aging also helps in analyzing the performance of the testing team and software development team. If the defects are fixed and closed in the very first software defect life cycle then this will let the Project Manager that its software development team is on the right track with right performance.
In order to keep track of the things discussed above the organization should have robust test management systems or tools. Defect Aging with manual work will be cumbersome to manage; the tools and TMS do it for you easily. The test management tools keep track of the defect status, who changes it and when changes it and this way it gets automatically find out that how many times the software defect life cycle have been performed on any particular defect.