The change isn't necessarily bad. It can be tho. That's why I recommend buying the mic used because change has most likely already occurred. That way, the sound of the mic when you first test it is more likely to be the sound of the mic later on. But each individual mic will sound different when they age. You can't just listen to any used mic and assume that all mics of that model number will sound like that when it ages. You have to listen to the actual mic you're buying and decide whether you like the sound or not. I wouldn't buy any used mics without hearing them first tho. There are a lot of factors that can make ANY mic sound like shit after being handled.