Yes, it's possible!!!!
I had a friend who was on cc before me but never bought premium, another one that i tried to get into it and who might have played it like for 6month and left... I gave them some premium 3/6month premium prizes I won to see if it wold make them sstay but it didn't work.
last september I went to visit some friends in spain, one of them saw that i was playing cc and he loves risk, he opened an account and has been playing since and i just saw that today he bought his premium! I now might be in trouble with his wife and his 2 kids!