yeah when it stops working.
Then get another one.
Are you thinking if you change it they wont be able to find you?
As far as i can see there is no need to worry.
A mac address is like a phone number that is attached to the phone and not the address.
They don't know where it's coming from.
like when when ur current mac dies u need to obviously give it a new mac like or when u want a faster speed other than that u should be cool unless someone dont pay there bill u should have it for a fair while