There is not a certain time for the powder to come off.Basically the fanning powder will come off when you play arround with the cards, doing riffle shuffles, springs, etc.Even if you do so, the powder won't disappear completely(I think so).You can also try to clean every card with a piece of cotton (I used to clean my cards like that in the beginning when I had only one deck

)The bad thing is that Tally - Ho Viper is a black deck, that means the edges of the borders will become white.This may affect your second deal performance, making it more noticeable for spectators.