As I understand it, you lose your original sign up date if you change your SN...
Unless you sign up to FR:
at home
at the library
at McDonalds
at Starbucks
ad Nauseum...
Even if the MAC number was captured/submitted on sign-up, the number of handles you could submit is only limited by the number of devices you own (or, throw-away phones you buy).
So, what?, one person can have 100+ handles on FR?