According to the non-answer I got when I questioned my US Senator, apparently forever. My solution?
I bought a 'call blocker'. Search with Google, and you'll find one that is suitable to truly handle this constant badgering by phone that the government passes laws to stop, and then does nothing to do so.
My Credit Card company used this number to call me earlier today to reset my pin number because it had expired, all I had to do was type in my credit card number in on the phone with them! And it must have worked too, because when I went to the 7/11 to buy a can of Copenhagen my card wouldn't work, and I had to pay in cash.
Called on my cell, which is on the federal DNC list. Have also received this same call on home land line which is also on DNC list. I will report this number to my state Attorney General.