How is the long term stability of the Manger sound transducer?

After the burn-in phase of 24 hours there are no more measurable changes. You might have the impression of further changes, but be aware that also your ears needs time to get adapted. All used materials in the Manger Sound Transducer are long term and UV stabile and without any plasticizer. You can be sure, that you will still have a joyful listening in 20 years or longer.