I have upgraded my Starkeys twice, about 7 years between each upgrade. All of the original aids still work as well as they did, but are each is a little less clear because technology, especially discrimination (only it's sound, not metal!) improves. I'm pretty sure I could still be wearing my 20 year old aids. Good discrimination filters out much of the unwanted noise and I can sometimes actually hear better than people with normal hearing in noisy environments. However, I don't use my aids when wearing headphones for MDing. For 2 reasons. I lost an aid (but found it later) when I took my headphones off to dig and don't want to repeat that. And my detector is plenty loud enough without the aids in.