Ecco la conferma dal sito di voipcheap:
http://www.voipcheap.com/en/free.html
"VoipCheap Freedays

If you buy credit, you will get 90 Freedays (unless stated otherwise). This means you can call all countries in the free destinations list for 90 days at no costs. When the 90 days are over, you will keep your credit, and a minimal rate (for instance 1 cent/minute) will be charged for the free destinations (this rate depends on the country and will one of these days be displayed on the rates page).

And it gets even better: If you top up your account before your Freedays are over, we will add (instead of overwrite) your Freedays up to a maximum of 365 days. For example: if you have 40 days left and you bought some credit, you will then get 130 Freedays."