As many times as you want, it has unlimited number of uses.
GREAT I THOUGHT SO!
all the things at the lingot store can be used more than once.
Exception - the streak freeze has to be "purchased" after each use and the progress quiz which I think they recently decommissioned was a 1 time use also. I'm hoping they bring the quiz (or something similar) back though!
Moreover, once you buy it you get it for ALL courses
Djenthallman, I love your profile picture! :P
Thanks, yours is nice too :)