Using the TB code
 

When you enter the TB code to activate your slots, is there a save or anything that needs to be done? Basically, do you have to use all of your alloted TB slots at once? I've read that some people have entered their code and then when they went back to TB it asked for the code again only to be told that it was invalid since it was already used. I'm trying to avoid that happening. I guess I'm asking how TB works after you enter your code initially?