I'm not talking about old damaged capsules, I'm talking about capsules that have been looked after but are old. And it would be usefull for the audio community to get some comparative measurements. Lets say that you find capsules deteriorate severely after 10 years. Don't you think we should know about that? If you are maintaining a Studer tape recorder that is worked hard, then you need to know that the bearings will wear and need replacing. Good studios do regular maintenance.
Microphones fall into this area.